If you are buying "full strength", i.e not premix, you will need half of the coolant systems full capacity listed in your owners manual. the remaining fluid should be plain water, preferably distilled. If you buy premix, you will need an amount equal to the systems capacity. Coolant is designed to provide maximum freeze/boil protection when mixed half and half with water. Confirm this with the tables you will normally find on the coolant packaging.

Buy two gallon premix antifreeze to be on the safe side suvs going hold more coolant.

Make sure that the coolant you buy is compatilble and is recommenned for your engine type also