That set doesn't contain the diaphragm.
Your vacuum pump does have a rocker arm.
Here you can see the inside of a vacuum pump:
the wheel in the middle of the two bearings rolls over a wavy flange of the timing device:
Here you can see the rocker arm again, the threaded part is connected to the diaphragm and pushes it up and down, sucking and pushing air.
Here you can see the vacuum pump with the cover removed. You can see the diaphragm. It is leaking, as there is oil on top.
If it is not leaking, it should be dry.
Under the small cover with the two screws are the valves.
You can make something like this to put the diaphragm under pre tension:
MB has a special tool, but that is probably expensive/unobtainable:
You can also use the wavy flange to put the diaphragm under pre tension, simply install the vacuum pump minus the top cover. Turn the engine until the rocker arm is fully extended. Than install the cover.