Alas, you bought the wrong rear camera!
The front unit is superb, and expects to see pictures from its companion 1080p camera for equally superb rear pictures.
Unfortunately the rear camera you bought is only 480 lines and not compatible.
You’ll need to do some detective work to find a rear camera that is 1080p, and has the same mini-jack connector as the original. If the connector is not to that standard it gets complicated with wiring and power supply voltage etc.