A meter* to check voltages is generally a good thing. Just randomly swapping things about without knowing what is, or is not, working is a short cut to some kind of disaster.
If a 3 pin connector is plugged in the wrong way round, in all present day radios that I know of, nothing happens**. A 2 pin, on the other hand, has the potential to do damage by putting reversed voltage into a circuit that was not designed to cope with that kind of mis-handling.
On a lot of modern radios, it is easily possible to insert a plug between the rows of pins. Got that T-shirt.
* Digital multimeters. They start surprisingly cheap, worth every penny.
**Maybe an outside chance that the bind pin might have been given a chance to do something strange.
