Help needed... Replacing Phone Cradle

Hi, I was hoping someone here could help me.

I bought my car (2003 SL55) with this fixed phone wired up (first photo).

I need to replace it with the Nokia 6310i cradle which I have purchased.

The problem is, as you can see, (second photo) I can only find an input for one connector (the one circled in red) and cannot find where to connect the other cable (circled blue). The phone and cradle will not work when only the one lead is connected. (The one input is shown in the third photo).

Can anyone please help?

Thanks