You need to look on the unit to determine the proper refrigerant to put in. Usually there is an indication on the compressor
itself. Also, you need to be up to speed on using a refrigeration
manifold, the high and low pressure sides, appropriate fill and running pressures, etc...
This type of work can literally kill you if you aren't 100% sure what you are doing.
You might need to read up on Richard Kollmann's site and get his book. It's called "Do it Yourself Refrigeration", but a refrigerator
and an air conditioner are the same thing. He has a section for a 1/2HP A/C compressor
. Same thing as most air conditioners.
BTW: It's R-12 you are probably looking for. I has some, but recently got rid of it, sorry.