ac recharge on 1993 Chevrolet S10

I am not sure ig the ac on my new used truck-- the fitings on the ac have been changed so Im not sure if it is old or new freon --- plus I am not sure how to hook it up--

Asked by for the 1993 Chevrolet S10
The refrigerant is defiantly R134a. But I have not got access to information that shows clearly where the charge ports are to connect the air conditioning pressure gauges.