The copper tube that is bare looks like the high side line it goes to the condenser coil. That looks like 3/8 copper. I can't see the suction line in any of the pics it must be insulated. It will be the other line coming off the compressor. Ps the 3/8 copper will be hot when running. They used to make saddle valves but I have not seen any in a long time and they tended to leak.
Wayne
Wayne