Hi Welcome to Justanswer.com
Please follow thebbelow steps (Given steps for both windows and MAC)
To copy all the items in your iTunes library (including the iTunes Library file that holds all your playlists, playcounts, ratings, and other data) to your external drive:Quit iTunes.Locate your external drive.Mac: On the desktop or Finder sidebar.Windows: In My Computer.Locate your iTunes folder:By default, the iTunes folder is located in:Mac: Finder > username > MusicWindows XP: \Documents and Settings\username\My Documents\My Music\Windows Vista: \Users\username\My Music\Windows 7 or 8: \Users\username\Music\If the iTunes folder is not in the default location listed above, find the iTunes folder by following these steps:Open iTunes Preferences:Mac: Choose iTunes > Preferences.Windows: Choose Edit > Preferences.Click Advanced.The location of your iTunes folder will be listed in the "iTunes Media folder location" box.Advanced preferences windowDrag the iTunes folder to your external drive. This can take a while if you have a lot of items.iTunes folder selected in FinderWhen the transfer is complete, your iTunes Library will have been successfully copied to your external drive.
Let me know how it goes .
OK I See
It will be better and quick if I can access your computer remotely to fix the problem ..
for that please follow the below steps
Please open the below link URL in browser
and then click on I agree button .
After that click on Download link to download a file and run it