What do I do to keep my new games if i bought games on my ipod touch and plug it in to sync it but it says it isn't synced to this computer yet?

on iTunes there is an option that let you export all your apps to the computer and then you can sync it... with your iPod plugged to the computer, open itunes, go to Files and if not mistaken the the option is above Exit, it say Transfer(export) all your purchases.