The G100 pins that are needed are pins 21 (RX), 22 (TX), and 20 (Ground) as per the harness diagram:
Please be wary of the orientation of the diagram, as on the opposite 'wire side', 'wire 24' would be on the far left rather than the far right. The DB25 male pin out is as below:
Please note the orientation of the diagram. When soldering, you shall do so from the other side, and as such pin 1 will be on the far right, as opposed to the far left, from that view.
You will need to solder the RX wire to pin 3, the TX wire to pin 2, and the Ground wire to pin 7. You can now plug the DB25 into the back of the base station,