Did you actually import the music files (from the iPod) into iTunes? In order to sync, they have to be in iTunes - not in a folder on the desktop.
If you did that, when you connected your phone to iTunes, did you then go to the Music tab an ensure each one of the new songs has been checked? If they are not checked (or are not in a playlist that is then checked) - they will not be transferred to the iPad on the sync.
Marilyn