wiring harness for grundig delhi sat nav

hi all
I am new to this so bear with me please.
does anyone know which wires/connections I need to connect a reversing camera to the head unit.
the car was originally fitted without sat nav but the unit I am looking to install has the sat nav . both are saab units.
the sat nav unit has 4 sockets at the back and the old one has only got the 2.
anyone any ideas
thanks

There is no option for reversing camera on the Saab Nav radio. Not sure what the 4th connector is for, but the 3rd connector needs 1 wire connection to the speed pulse otherwise the nav is a little laggy.

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