99 suburban a/c low side pressure port

Where is the exact location of the low side pressure port ( to recharged a/c) is it on top of the compressor or on the side of the accumulator?

It's on the line that goes to the fire wall. The two ports are next to each other
on top of the compressor and it is the one on the right. It is also the "cold" one. The "high" side goes to the condenser coil in front of the radiator: "hot" one.