What kind of freon does it take for the 2000 Solara?
It takes R134-A.
You don't. The 2000 Saturn refrigerant is not Freon R12 it contains R134a. Add it at the Low pressure port. You have a leak or it would not be necessary to add refrigerant. It is illegal to add refrigerant to a system with a leak without first repairing the leak. Take it to a professional and have the leak fixed.