This article explains how to find, consolidate and backup your iTunes media folder in iTunes 12 and later.
How to Use External Hard Drives for iTunes
Back up important files so that you are prepared in case your computer crashes or hardware fails. A backup is especially important considering how much time and money you have invested in an iTunes library. To back up your iTunes library, you will need an external drive with enough free space to hold the library.
If your iTunes library files are in one place and organized, it’s easy to back them up to an external hard drive. If not, you’ll need to locate your iTunes media folder and consolidate them before backing them up. To back up your iTunes music to an external hard drive:
Locate your iTunes folder based on the location you specified in iTunes.
