How to transfer my old mp3 files from my iphone 7 to my imac

Apple music has just deleted my entire itunes library from my iphone 13 when I connected my phone to a newly reset imac (locked up so had to reinstall OS)

After connecting my phone to the newly installed mac my non-apple files disappeared.

However, luckily I have my old iphone 7 which still has my original mp3 files in itunes which I have collected since first owning a mac about 25 years.

These albums and playlists included old vinyl records transferred to mp3 as well as CD,s tapes etc.

How can i transfer my apple music folder to my imac without apple wiping them again.