You have the pickup connectors already, just someone cut them not realizing they were modular. I've marked them in blue in the attached image so you could splice these on and protect with shrink tubing. You plug one pickup into each of the volume control boards.
The second image has an unconnected wire - can you tell me where the other end is? I think it may be one of the wires that connects the two volume boards that I marked in a white circle in the third image. The blue circles in image three show a wire that is cut very short on the small volume board that you will need to replace. Once the two volume boards are connected, the 3-pin and 2-pin connectors are already connecting the 2-volume harness to the filter module.
Can you post a picture of just the solder side of the smaller of the 2 volume boards? The pots mount directly to the board. You will need to use a desoldering iron or solder wick to remove the old pot first. Do be careful - if you overheat when you are removing the component, you can burn up the trace and trash the board.
The pots in the 2-volume Activator are 100K audio taper. You might be able to find this locally. If not, I do have spares.