Do I need to convert my air conditioner system in my '96 Bronco?

After my air conditioner stopped blowing cold air, a friend and I tried to buy more refrigerant, but the hoses wouldn't hook up correctly. Apparently the area to add the coolant is smaller than the hose. After talking with a few friends, they believe that maybe I have the old R-12 system and not the 134. But after calling a mechanic to get a quote on converting it, they said that a 1996 Bronco should have a 134 because the cut off date was 1994-1995. Who is right? I know absolutely nothing about cars and vehicles. Please help!!??