i have a mazda b2300 and the refrigant copletely leaked out and i need info on how many cans of 134a do i need approx. to fill the system.

 

(1) You need to fix the source of the leak
(2) Since all the refrigerant leaked out, you'll need to replace the drier/accumulator
(3) You'll then need to attach auges and pull a vacuum, then add refrigerant.
(4) A sticker under the hood should list R134a capacity.

If you don't know how to do all this: DON'T.