Electrical – Which numbers identify inputs and outputs in circuit breaker

The trivial way to do this is to buy an off-the-shelf power strip with a switch and 15A circuit breaker, and plug that into a 15A-or-more GFCI outlet.

If you don't want to replace the existing outlet, you can do what I did: Buy a standard 15A 3-prong power cord, a GFCI, a box with an outlet faceplate, and a strain relief. Knock out an appropriate size hole in the box, install the strain relief, run the power cord through that into the box, wire the power cord to the GFCI (with ground to the box as well as to the GFCI), close the patient. Bingo, portable GFCI that can be plugged into any 3-prong outlet.

Or you can look for a power strip that includes its own GFCI. Some do exist.

Yes, you can wire this up from scratch. But if you have to ask how to do so, it's safer AND not significantly more expensive to just plug together parts that are already UL-certified.

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Having said all that, the answer is that there are several possible arrangements that would work but the one I'd set up for you would probably be:

Hot from wall to switch, other side of switch to breaker, other side or breaker to GFCI Hot In.

GFCI Controlled Hot Out to hot of other outlets. NOTE THAT THIS IS A DIFFERENT CONNECTION FROM GFCI HOT IN. READ THE INSTRUCTIONS CAREFULLY. DO NOT GET THIS WRONG.

Neutral from wall to GFCI Neutral In.

GFCI Controlled Neutral Out to neutral of other outlets. NOTE THAT THIS IS A DIFFERENT CONNECTION FROM GFCI NEUTRAL IN. READ THE INSTRUCTIONS CAREFULLY. DO NOT GET THIS WRONG.

Ground from wall to ground connections of GFCI and all other outlets.

If the reasons for doing it this way aren't obvious, STOP and get someone more experienced to work with you.

I can see a SquareD logo on the side, and the red indicator window on the front makes it look like a Square D QO 20-Amp Single-Pole Circuit Breaker, model #QO120CP:

The overall shape of the breaker and orientation of the contacts on the back seem to match your breaker.