Syncing iPhone with new MacBook Air M1

My iMac, which I had my iPhone containing my music synced to, died. I replaced it with a new MacBook Air M1. I want to be able to sync my iPhone with my new computer, but when I try it says it's going to delete all my music from my iPhone. The music from my iPhone is from all my CDs that I had imported on my dead iMac. I had a copy of the iTunes folder from my iMac, which I tried copying to the music folder, but that didn't resolve my problem.

How do I unsync from my iMac, which no longer exists, and sync to my new computer without loosing all my music.