Referencing the picture you posted yesterday, the pin with the small blue wire soldered to it is the base (pin 1). The other pin (pin 2) is connected to all 4 of the emitters. This is actually ground with respect to the drive power supply. You will notice that the transistor body (tab) is insulated from the heat sink and these are actually what is going to the motor leads. It occurred to me it may be necessary to remove the transistors from the parent circuit to test them properly, I am not sure. I think you will be able to find one that measures differently from the others, this will indicate a failed transistor. If they are soldered, I would hold off on that until you run the tests. Some machines, including mine, have already been switched out to sockets so that no soldering is necessary. Lots of machines have this modification which should tell you how often the transistors are blown.
You are mainly just looking for continuity so the range is not too important. It should either be quite low resistance or it will be many million ohms depending on if it is conducting or not. 20k range should be fine. If it says 20k, its probably much higher than that (can try switching to the 200k range to see) if it says 0 (or close) it is conducting.
Matt