Car Seat

So I recently found out that I am pregnant. This will be our 3rd baby but now we are worried. We are not prepared as in we don't know if we can fit a 3rd car seat in our car. We have a Subrau B9 Tribeca and already with the 2 car seats we have a 3rd one will not fit. Before we go on and ask my father if he can help us out with getting us a bigger suv is there any car seats that can fit in our suv? We don't mind buying new ones we just don't have the money for a new suv. Thank You