Well that kinda narrows it down. I guess that there are no limit switches on the mechanical frame?
You need to visually check this yourself as you have the board in your hands, but from the photos, it looks like those 4 pin connectors plug in to those 4-pin male headers below the reset button.
From what I can tell from the photos, ignore the first 4-pin male header (by the mounting hole), a motor cable then plugs into the next 4-pin male header (next to where the silkscreen printing says J2) , then skip a header, then motor #2. As for motor #3, I can't see where that plugs in. You should be able to follow the tracks on the board to the connector. You may have to remove the driver board if the tracks are on the top.