Go to web site of the Tire Rack. THey will have best tires at best prices and if you cruise through their web site, you can read and learn many things about tires, tire ratings, and better tires that will last longer.
You can look on your current tires for the size that are on them such as 195/75R16. Your number may be differnt that the example I listed. But that will give you an idea of what you are looking for. You will find this on the side wall of the tire.