What is the part called on a hand gun where you load the bullets?
Oh, Lord! You’re asking about revolvers. And it’s not clear that you’re even asking about loading bullets. Old cap-and-ball revolvers load powder and bullets into the front of the chambers in the cylinder. Those went out of favor in the 1870’s. Modern revolvers tend to load self-contained metallic cartridges (case with primer, propellant, and bullet all in a unit) into the rear of the chambers. Some break open from the top, others swing the cylinder to the side, and still others (such as the famous Colt Single Action Army) load by swinging out a “loading gate” to allow access to the chambers. Keep plugging here. You need to learn proper terminology to learn these things, so this sort of “stupid question” will eventually allow you to get better information. I’ll probably not be the only one to give you a harsh answer, but don’t let that dissuade you.