iPhone asking for password after restore

A few months ago my boyfriend's phone broke so I restored my old iPhone 7 to see if he wanted that to use. I reset it through the settings app on the phone itself. He ended up not wanting it anyway because he prefers android devices (lol). Anyway, I've been wanting to try and restore the phone from a backup on my old PC associated with the device that I used to sync it to all the time to access old photos and stuff. However, the phone keeps insisting I put in a 6-digit password that I never set myself. I have literally no idea what this could be since I've only ever only used 4-digit passwords in the entire time I've been using Apple devices. Is there any solution at all for me or is this a lost cause? I plug it into my computer and nothing pops up and I can't get past the password prompt on the iPhone.