you most likely have r12, which is the older type. ac systems are measured in pounds. most cars take 2-4 pounds of freon. I think you are supposed to convert to r134a to save the environment :ghey: so its really hard to find r12. at our shop it costs like $60 a pound. r134a costs like $5. converting is hard though because you have to decharge the system, then change a bunch of seals so that the new seals are clean and ready for r134a. its best to take it to a shop.

hope that helps a little bit I even confused myself