How do I log into my Apple ID if I forgot my old iPhone passcode?

See the Apple Support article(s) below for IOS 15.2 or later..

Passcode - How to reset your iPhone, iPad, or iPod touch when you forgot your passcode (IOS 15.2 or later).  *

ASC YouTube for how to restore your iPhone if you forgot your passcode - Apple Support.  -

See the Apple Support article(s) below for earlier than IOS 15.2 . 

Passcode - If you forgot the passcode for your iPhone or your device is disabled.    *

See if anything here helps.  If necessary, you can use account recovery as explained in the link at bottom of the article.

Verification code - how to get one and sign in with two-factor authentication.   *