2007 prius aux cable install issues

Watching the following video l thought l would do the same..

So l ordered a toyota aux cable thinking it would be a plug and play fix


When l got to the back of the radio l found that already a cable was plugged in the port l thought l would be using since the cable l bought would surely fit in there


So l am wondering... what does it do? I am pretty sure l can't just replace it with the aux cable that l bought. I'll most likely have to try to find an aux cable with a smaller jack so it will fit in the port as shown in the video...