How to get iTunes to copy music you import to a safe/internal folder
Launch iTunes then open Preferences, either from the Edit menu or by holding  Ctrl ⌃   ,  

In the Advanced tab, check 'Copy files to iTunes Media folder...'  



This may prompt iTunes to ask if you want to Consolidate existing files. If it does, say Yes.
If not, then do it manually afterwards, from File > Library > Organise Library.

This will grab all existing files from all locations except the iTunes Library &amp; copy them there.