How do I know what belt to get to skip broken compressor?

First of all take the old belt with you when you go to the parts store. Second, move the alternator in as far as you can so that you have maximum expansion available with the new belt. Then take a piece of string and run it around the pulleys and make the meeting spot. Now take it off and measure the length of the string needed to complete the loop. Go to the parts store and ask if they have a belt for that car without the compressor. They may have that in the books if the possibility exists that A/C is not available. But you can also if that does not work give them the length of the belt, they can see the type and width of the the old belt and fix you up with a new one.