Any chance you can take the 4 screws out of the side of the case and lift the lid and photograph the insides.
I use two of those generic cases for two adjustable 0-30v 0-5A power supplies.
Don't take the screws out of the front or rear cover, just the sides to lift the u shaped lid and photograph.
Interested to know which breakout board they are using and also any wiring as you need to configure the estop as mach3 won't move without it or without it being lifted plus you have a spindle and water pump which are probably connected to outputs.....
Thanks
I'll try to look for a manual for you but like I said those are rather generic cases....
https://www.ebay.com/itm/372638870695