Q: Erase data all data with outdated password apple

I am trying to set up my I phone 5S for my husband and they are asking for my old Apple ID password for that specific phone to erase all data. I have a iPhone 6s that takes my current Apple ID Passcode

Apparently another Apple ID passcode of mine was used in the past for this older phone and I have no idea how to retrieve that. It is not the pass code to get into the phone but the pass code to get the Apple ID because they asked for that to erase all data.