My laundry room dryer outlet is currently wired with a 50 amp 3-prong outlet, but has a 30-amp breaker on the main panel. I've been using the dryer in this outlet just fine for a year after moving in with a 3-prong 50 amp cord I connected to the dryer. My understanding is that these are typically used just for electric oven ranges. (Example of current outlet here: https://www.homedepot.com/p/Leviton-50-Amp-125-250-Volt-Shallow-Flush-Mounted-Single-Outlet-Black-R30-05206-S10/302480499)
EDIT: Based on updated photos, looks like I have L1, L2, N, and G to wire into a new 30a 4-prong outlet. In my exisitng outlet ground and neutral are wired together.
UPDATED: added 2 photos of wiring on existing 50a 3-prong outlet:
Is it okay to leave this in place? I know this no longer the practice for new work. I am about to buy a longer cord for my dryer, and was going to buy the same 50 amp 3 prong cord. The price difference for the 50 amp cord is minimal, so I'd rather leave this outlet in place.
Or, should I just replace this outlet with a new 30 amp outlet? If I do use a new 30 amp outlet instead, should I be using a 3 or 4 prong style? Is the dryer dependent, and wiring dependent? If I do replace the 50a outlet, it seems like I should be replacing the 3-prong outlet at 50 amps with a new 3-prong outlet at 30 amps.
Example of 30 3-prong I would purchase:
https://www.homedepot.com/p/Leviton-30-Amp-125-Volt-250-Volt-Shallow-Single-Flush-Mounted-Outlet-Black-R30-05207-S10/302480849
Best Answer
New, 30A 4-wire 4-prong (NEMA14-30) is the right, safe, and correct thing to do.
10-30 and 10-50 outlets were (finally) banned in new construction nearly 3 decades ago. Every now and again they manage to kill people. They can still be purchased "for repair only" of existing circuits with the wrong wiring, but it's really past time for them to go, and some folks do misapply them for uses other than that.
How easy or hard that is will depend on what the wiring to the improper 10-50 you have is. (So, turn off the breaker, and pull it out and edit in pictures of that.) The dryer will also need to be changed to remove the neutral-ground bond, but that is a simple change when you are replacing the cord.
Edit post picture: Incredibly easy to do this right with the wiring you have (though you'll have to check that the other end is wired correctly, and correct it if it isn't, to be sure.) So some idiot deliberately chose to do it wrong on this house in the past. You have a 4-wire cable with separate Neutral and Ground conductors. Get a NEMA 14-30 R and a 14-30P dryer cord, and check the wire connections at the far end of the cable (in the breaker box that feeds this.)