the block valves are the two valves that are on the liquid and vapor lines on the outer (condensing unit), they are used to pump down the system, meaning trapping all the gas in the condenser to remove open the lineset for anything ranging from service to replacement.
All A/C technicians know of these valves. And a proper vacuum pump is this which is available in Pakistan.

You can also improvise by using a rotary type fridge or freezer compressor.