If you are serious then all you have to do is look at your belt and count the actual ribs in the belt. Also if you bump the starter a few times and watch the belt it should have writing on it somewhere that will give you a key/part number that will help ya out a ton.

When they refer to the ribs they are referring to the actual ribs on the belt so just by looking at it and counting the ribs you can figure that part out.

Good luck.