forgot passcode on ipad air2

I am trying to trade in my dads old iPad Air2. He passed away in 2016 and I used it briefly and didn't want to get rid of his passwords so I remembered them. I stopped using it over time and now I want to erase the content so I can trade it in and get a new one for my mother to use. However I signed in with my passcode as I reset it, but then comes up with the 2 step authentication and I cannot remeber for the life of me what the 4 digit code is for that. I have 11 failed attempts and its stressing me out to say the least.

I have tried to reset using the recover method but this doesn't do anything at all. Is there a simple way to erase the ipad or am I stuck with a brick now?

Thanks in advance