One possibility. You'll have to use a meter/ test lamp to figure out which terminals are which. You should be able to "jerry rig" it to your air compressor to determine the terminals
With the switch "not pressurized" use a meter/ light to see which terminals show continuity. These two will be "one of them" NC, the other C
With the switch "pressurized" again use a meter / light to see which two terminals show continuity. These two will be "one of them" NO, the other C.
Pay attention between the two tests above to see which terminal you used in both tests, this one will be the C--common
So C is common
NO is normally open with no pressure
NC is normally closed with no pressure
You should use a pump relay, so hook the coil of the relay where this shows "pump"
"Starter" means you hood the "nc" terminal to your start wire going to the start relay which comes from the ign switch--that is the push on terminal on your start relay. This "fires" the pump relay when cranking
The n.o. terminal goes to your blue "ignition run" wire running to the ballast resistor