The Tribeca being a 5EAT should have Subaru HP in it, which is a full-synthetic. There are a few aftermarket equivalents...
4EATs before 2006 just need Dexron III, which is the most common and cheapest form of ATF (usually labeled as Dex/Merc). There are plenty of synthetic and name brand alternatives, but you're transmission would be better off if you spend a third as much, and change it twice as often.