Iphone 12 to 17 - all music grayed out

I upgraded from an iPhone 12 to an iPhone 17 Pro Max. Have an older iMac. Apple store tells me music is stored on the iMac, but the iPhone 17 not compatible with iMac. WhenI attempt to connect iPhone 17 to iMac, I receive a message that USB accessories have been disabled, as the iPhone 17 uses too much power.

Most music was owned by me; very little was purchased. Lists of artists and music appears on iPhone 17, but all music is grayed out and can't be played.

Had a phone call scheduled with Apple Support but got disconnected and no return call.

Have trouble believing that Apple conversion programs do not convert music????? Help.

What is the solution?