How do I transfer music from my iPad to my phone

You cannot directly transfer between the iPad and iPhone. You'll need to sync with a computer or you need to be a subscriber to Apple Music or iTunes Match (which will sync all of your devices)

Devices are synced from your computer to your device. Your music library from your computer is synced to your device. If you want your music on your phone, just connect your phone.

You didn’t really answer my question. Do I connect my iPad to my pc and sync, then eject my iPad and then connect my iPhone and then sync to get the music from my pc to my iPhone? I don’t want to mess up my music I’ve added to my iPad. Thanks.

Do I connect my iPad to my pc and sync the music from my iPad to my pc then connect my iPhone 12 Pro to my pc and then sync my iPhone with my pc?

You can just connect the iPhone to your computer. All of your music is in iTunes or Music app