How to get my Authenticator code back
Help me to backup my Authenticator code on my old phone back
iPhone 6s Plus, iOS 15
How Facebook authentication works, how two-factor works, and how to request codes to regain access:
https://www.facebook.com/help/148233965247823/
https://www.facebook.com/help/358336074294704?helpref=faq_content
https://www.facebook.com/help/148104135383285?helpref=faq_content
I'd expect you can use a code to regain access, and then configure the new iPhone as an authenticator.
If you have issues with this, check with Meta Facebook support.