Syncing iPad Apps to iTunes

I have an iPad for work that a couple other people used before I received it. I am trying to sync my apps to iTunes, but have run into a snag. If I check "Sync Apps" in iTunes, it tells me it will replace all apps on my iPad with those on my MBP (I don't have any apps on my MBP). I do not want that. In fact, I want the complete opposite. I want iTunes to backup the apps I've installed on the iPad.

Isn't there a way to do this? I'm rather confused as to why it won't just back them up for me.