Where is the high pressure port for ac on a 1996 Volvo 850?

The high-pressure AC port on a 1996 Volvo 850 is typically located on the compressor itself. It's usually a thicker line than the low-pressure line and will have a cap on it. However, without seeing the specific engine bay of your car, precise location on the compressor is difficult to describe further. It's best to consult a repair manual specific to your 1996 Volvo 850 model year and engine type. A diagram in the manual will clearly show the location.