iphone unavailable /second hand iphone12

i bought this phone from a ederly lady about 2 months ago she had gotten a new phone and wanted to sell this one she gave me the passcode and everything i unlocked it everything was fine i never signed into it as i had one i was using but i always tend to brake my phones so i kept this one for back up. now i have forgotten the stupid code and unfortunately she has since passed away and i have locked the phone it says unavailable i can put it in recovery put it doesnt show in icloud or apple devices how can i factory reset this phone as i am in disparate need of a phone for school my entire college information was in my phone please help a dumb college chick out

IPhone12 unavailable but will go into recovery mode i am useing windows 11 Microsoft pc i have Itunes Icloud Apple devices and Apple Support app it does not show on any of them