I have lost all of my music on itunes.

Question

I have aton of music on itunes and now nothing shows up when I open itunes. Help!

Answer 1

What you have on your computer is an iTunes library, not an account.  Your "account" that relates to iTunes is your Apple ID.  The distinction is important, because you can sign in with your Apple ID to the iTunes Store, and re-download most previous purchases from the iTunes Store, at no cost.  From the iTunes Store Home screen, click on Purchased under QUICK LINKS.
Syncing with iTunes generally goes one way, from the computer's iTunes library to iPod.  You cannot transfer song files from iPod to computer using iTunes, except for songs purchased from the iTunes Store.  However, there are third-party utilities that can transfer from iPod to computer.  If you do an Internet search on something like "ipod transfer," you should get some links.  (The CNET article seems to be popular.)
Once the song files are on your computer's drive, you can add them to the iTunes library.
I have lost all of my Music, books from my ITunes account on this new computer.
NOTE:  If that new computer once had all of your content in its iTunes library at some point, and then you "lost" it for some reason, the media files may still be on the computer. 
Look in your user home folder's Music folder.  In the Music folder, look in
/iTunes/iTunes Media/Music/ - For song files, organized by Artist and Album.
/iTunes/iTunes Media/Books/ - For books, etc...
If those iTunes media files are already there, but not in your current iTunes library, you can add them to your current iTunes library.