I think you are referring to the cabin filter. If so, there are two inside the passenger side, which require removing the glove box.

http://autorepair.about.com/library/a/1g/bl038g.htm

Also, follow the glove box removal. Make sure to use something that will not scratch the panels, such as putting cloth over a screwdriver, etc.

One air filter in the engine bay on the passenger side (6th gen).