iTunes (Music) library onto Seagate Backup Drive?
How to backup my iTunes(music) library onto my Seagate Drive and then delete my iMAC Music folders(s))
iMac 21.5″, macOS 10.15
Hey! I have done a similar thing with my iMac when I got a new one, what I did was plug in a USB (or in your case the backup drive) I open iTunes and I clicked on a song and made it blue and then I clicked Command+A to select all and then dragged the music files to the device (which should be a white icon on your desktop) and waited for it to transfer. I hope this helps!