Here’s the image of the pinout from the linked manual:
Based on that the audio cable will look like this:
GX16-6 pin 1 (MIC) → 3.5mm TRRS ring 1 (RIG_AFIN)
GX16-6 pin 3 (PTT) → 3.5mm TRRS ring 2 (RIG_PTT)
GX16-6 pin 5 (GND) → 3.5mm TRRS sleeve (GND)
not clear if EXT. AF is the received audio. If it is then:
GX16-6 pin 2 (GND) → 3.5mm TRRS tip (RIG_AFOUT)
otherwise
3.5mm TRS tip (EXT.SP) → 3.5mm TRRS tip (RIG_AFOUT)