If the range does not have instructions for wiring with a 3-wire plug with hot1-hot2-neutral, then improvising would be out of the question, both for actual safety and for satisfying the code.
Without the range installed it is not that difficult to remove the receptacle and put in a 4-wire 50-A receptacle (NEMA 14-50). You can fit a 40-A or a 50-A breaker depending on what the wire allows, but can fit a 40-A breaker even with #6 wire. You would add a #8 or #6 copper ground wire (to match the existing conductors) going back to the panel. Or if it is available, connect by tap onto the heavy, uninsulated ground in your attic that goes back to the panel. Use a split bolt connector to tap. The added ground does not have to follow the route of the existing conductor.
First examine the contents of the box. Of course, shut off the breaker, then pull out the existing 3-wire receptacle and see what size wire you have. How many conductors do you have? Probably just three, but maybe you'd get lucky and find an unused ground coiled up in the box.
NEMA 14-50
EDIT
You should at this point contact your local electrical code enforcement and ask them about the approach outlined above. If this is allowed, then it would not be dead easy to fish a ground down into the wall and into the existing box. Someone here would have to tell you the practicalities on how to do it. What may happen here is that you will learn from the experts here what is a reasonable arrangement, and if you have never done this before and need it done without delay, then you might have to hire an electrician, but at least you would have in mind your instructions to the electrician.
If you have 3 wires coming from the wall (hot hot neutral, no ground), then you hook the wires to the 3 terminals that you see. Note the odd little strap linking the neutral stud to the chassis of the range. It is "grounded" to neutral. Any fault with the neutral wire will energize the chassis at one of the hot voltages. Yikes.
If you have 4 wires coming from the wall (with ground), a little work is required, but this increases safety. First you remove that odd little strap, as you will be connecting neutral and ground separately. Then you attach the ground wire to that green terminal you just removed the strap from. That lug in your photo is a fine method to do that! Then you connect hot-neutral-hot to the 3 studs, much like the above.
The T&B lug connectors in your question are certainly good for 40A. UL would not let them label for #8 wire if they were not good for 40A. They are undoubtedly a good choice for ground wire. For "hot" wires, after torquing their screw to spec, I would wrap them with shrink tubing or electrical tape.
I agree with 'Bat that the T&B connectors are a little concerning as far as hitting the chassis or something else. That compartment doesn't apear to have a cover, and they seem awfully exposed. See how they fit (you are sure to be able to use one) and make a judgment call. As far as the ring terminals he is recommending, you will need larger ones that fit on #8 wire. They do make those, but not necessarily insulated. Then you can shrinkwrap them with shrink tubing. Just use black.
Uninsulated is good, though, as you can solder them with a nice large soldering iron, not the electronics pencil types but either the inductive gun type or the really big 16" long types. For the solder, go out of your way to find old fashioned lead solder (non-RoHS; RoHS compliant unleaded solder will crystallize over 10-20 years, it is a death sentence for any eelctronics built that way). Do not use plumbing solder, it's acid core and not lead.
On a 3-wire connection, the neutral is so important that I would not trust a ring crimp terminal alone. I would use one of the T&B lug connectors, it doesn't matter if that makes contact with chassis.
Best Answer
For a safe and code compliant setup, everything has to be compatible:
What you can use is determined by the range; the manufacturer's instructions will state what operating voltage and ampacity is suitable for the electrical circuit.
The breaker is the main safety device, it protects the wire from starting a fire if there's a short or overload. If you have 10 gauge wire, you're probably limited to a 30 amp breaker. Most ranges require a 40 amp or 50 amp breaker.
The receptacle has to be suitable for the ampacity of the circuit. The NEMA specifies a receptacle configuration for all the various circuits / ampacities. Ranges usually operate on combination 240/120 volt circuits, and either 40 or 50 amps. Many will also run on 208/120V circuits, and some will only operate on 208/120V circuits.
The range is usually sold with the NEMA cord and plug for the NEMA receptacle that's suitable for the type of circuit your range requires, if it is not included with the range, the appliance store will usually sell one that's suitable per the manufacturer's instructions. They may sell you both a three prong and four prong cord and plug set for your range; older homes often have three prong circuits with no safety ground, and have three wire receptacles. Newer work will have four wire 120/240V range circuits with four wires circuits and four slot receptacles. You would (carefully) follow the manufacturers instructions to attach the three-wire or four-wire cord to terminals in the range.
Unless your range is made for a 30 amp circuit, you're probably going to have to run new wire. Even if your range operates at 40A, I'd install a 40A breaker and receptacle with wire capable of 50A. There's nothing wrong with oversizing the wire, and this way you can upgrade the stove by changing the breaker and receptacle without changing the wire.