Benzoyl peroxide usage?

I’m writing this in English because I honestly have no clue how to phrase this in American—I'm still getting my bearings here. But anyway, I think you guys know what I'm talking about... some kind of cream containing Benzoyl peroxide. So, where can I actually pick that up in New York City? Is it something I grab at a pharmacy or just a regular drugstore? I haven't been in the area long, so I'm still figuring out how everything works.🙂
Roughly how much am I looking at paying?
Thanks!

Antopar gel

...it used to hold 5% and 10% market share...but you can't even find it on the shelves here anymore