how do i remove my old apple id

Do you remember the password so you can sign out of the old ID?

Use the article below as a guide of where to sign out of the old ID.

What to do after you change your Apple ID or password - Apple Support.  

Try this -> go to Settings -> Mail -> Accounts -> scroll & tap the email address you want to delete -> scroll down & tap Delete account.

Check also -> Sign in to your Apple ID account page and edit / update your Apple ID details.

https://appleid.apple.com

-> edit your Apple ID.