Forgot an old icloud account
what do i do if i have two different icloud accounts and don’t remember the old one from an old phone?
iPhone X, iOS 13
If you are locked out of your Apple ID account you can go to https://iforgot.apple.com
This will provide you with the recovery steps you put in place for this situation.
Here are some support articles that should help:
If you forgot your Apple ID password - Apple Support
If you forgot the answers to your Apple ID security questions - Apple Support
If your Apple ID has been locked or disabled – Apple Support