iPhone 13 asks for a 6-digit password I don't have
I exchanged my Iphone 13 to an Iphone 15 two years ago. Now I would like to restart the 13 again. However, it asks for a 6 digit password, which I don't have. I have never had more than 4 digits in the password for opening the phone, so I have no idea what it's asking for. Can someone advise on how to solve the issue?