Old Email on apple store
I used to have a different email for the AppleID and the Apple Store. I now got a new iPhone and some apps are asking me for the old one, but I can't retrieve the password, so I am not able to use the apps.
iPhone X, iOS 14
If you forgot the Apple ID password, enter the Apple (iCloud) ID, and click Forgot Password. See if you can get a Rescue or Notification email option if necessary. Link to contact Apple Support at the end of the 2nd article.