Hi everyone.

I've recently built a Socket 7-based Pentium system using a baby-AT motherboard I preserved from my youth (an Epox MVP3C-M for those interested).
Everything works nicely, but I can't use my optical PS/2 mouse for the simple fact that I'm missing a few of the port brackets - chief among them the one containing the PS/2 port for the mouse. The motherboard has a 5-pin PS/2 header to connect a port to, and getting ahold of a new PS/2 bracket or fashioning one myself from a female PS/2 connector is definitely doable - however, I have no earthly clue what the layout of the 5-pin header is. The manual sadly doesn't go into detail on that particular header.

Having spent a few hours scouring the internet for the standard layout of this 5-pin bugger, I've come to the conclusion that there simply were no standards for this back in 1998 and if I wire this thing up incorrectly I may end up damaging my PSU, frying my mouse or both. I've read a good number of threads about the subject here on Vogons, too, and they all recommend using a multimeter on the motherboard to identify the GND, 5+ VCC, and Data pins on the header. I do have a multimeter, and while I've spent a good deal of time watching YouTube videos on learning the basics of this thing, I'm still kind of lost for this particular task.

Since I'd prefer not frying my otherwise meticulously well-preserved board by accidentally short circuiting something by inserting probes where they don't belong, I would love it if someone with actual understanding of this could guide me a bit. I'm not even entirely sure what to set my multimeter to, which holes to plug the probes into and what I should be seeing on the display in order to identify each pin. Heck, I don't even know whether the PC should be on or off when I do my measurements.
This is the particular model multimeter I own if it's any help: https://www.amazon.co.uk/gp/product/B00GJW6LZ6

I would be eternally grateful for any help you might be able to provide me with, oh wise sages of all things hardware. I throw myself at your mercy! 😀