Sync iPod to computer

I have bought 4gen iPod about 4 months ago. Then I add the song to my iPod whole of them are from CD album. Today all of my CD are gone and I wanted to save my songs to my computer again. I tried almost every way using software or save manually but these all doesn't work. Could you help me?

-iPod can connect to iTunes

-I can listen iPod's song with iTune

-iPod still working. I can listen to music

-I can't drag my song out from My Music

-I can't see any folder in iPod's drive [normally I can see them but today I don't]

-I can't see any backup or sync folder *user*/My Music/iTunes , I only see my iPhone 5 and my iPad 2

-I used lots of helping software but it all said error