How to convert USB to PS/2?
Many USB keyboards (certainly older ones, though almost certainly not wireless ones) are also PS/2 keyboards.  The wiring of the cable is all that differs, and the chip in the keyboard changes its behaviour depending on how it's wired.

A simple USB to PS/2 adaptor is merely a USB socket and PS/2 plug wired together in a certain way:



So that's:


5V to 5V
D- to Data
D+ to Clock
GND to GND


It may work with your keyboard, or it may not. All you can do is try it and see.