I purchased these for an existing controller.

200W Spindle Speed Control Board ,Driver Board and Interface Board For TONSEN Mini CNC Engraving Mahcine Accessories-in Other Electronic Components from Electronic Components & Supplies on Aliexpress.com | Alibaba Group

Actually, I just needed two stepper controller but the cost of two stepper, I just added $20 more and got the whole thing.
Now I have a spare stepper controller and control board for future.

However, this does come with a spindle speed control board, top right corner board in the picture. I would like to put this in place of the manual variable resistor control knob and control it in MACH3.
Anyone has this existing setup on their gear? I believe these comes in upper model like 3040 and 6040. I own a 3020t.
I just need the wiring needed to enable the spindle speed control with the main controller.