I have three different passwords on three devices. How can I merge them or delete two of them?
I have three devices with three different Apple IDs. How do I merge them?
MacBook Pro (2017 – 2020)
Your Apple ID is the personal account you use with all Apple products and services. It includes the email address and password you use to sign in, as well as the contact, payment, and security details that you use with Apple.
You can’t merge multiple Apple ID accounts.
See -> Sign in with your Apple ID -> Sign in with your Apple ID - Apple Support