Downloading itunes 11

I downloaded the newest version of itunes, but I can't install it because my current version isn't updated enough. I think I have 10.6.3 (I was doing it last night at home, but I'm at work now.), and I need 10.6.8 in order to install 11. Any ideas?

I tried checking for updates for my computer and for itunes, but none show up. So I don't know what to do.