Stuck with old Apple ID

I need help. I just got an Apple Watch and I can’t log into it. It keeps asking for a very old Apple ID that I no longer have access to, and I don’t know the password. I also can’t reset the password anywhere.

My iPhone is signed in with a different Apple ID, so I don’t understand why this old Apple ID keeps popping up on both on my phone and when setting up the Apple Watch. I can’t figure out how to remove it or switch the Apple Watch to my current Apple ID.

I’m really stuck and don’t know what to do.