With macOS Catalina, Apple renamed iTunes to Music.
In this guide, we use the terms interchangeably.
Older versions of iTunes/Music may contain this option in theAdvancedtab.
To view the consolidation screen, select theFilemenu, then selectLibrary>Organize Library.
Enable theConsolidate Filesoption, then selectOKto copy files into one folder.
To do this you will have to check that iTunes is not running.
However, Apple has had this capability removed for more recent versions.
This is so you could easily copy the media folder by dragging and dropping it.
Drag the iTunes/Music folder from your gear to your external drive or hard disc.
Wait for the copying process to complete.