Kenwood DNX4230DAB missing SD card

Hello everyone.

I am hoping someone can give me some guidance here, I recently bought a Mitsubishi L200 with a Kenwood DNX4230DAB factory fitted.
It does not have any map card installed in the SD card slot, and when I press the nav icon on the touchscreen says 'no maps found'.
I am assuming that this device does not have any internal memory for maps, and relies on the SD card being present.
I have updated the firmware in the unit to the latest version, and the navigator software to the latest version, could anyone give me a clue as to the folder structure of the SD card so I can try to re-create it, I have downloaded some unlocked maps but not sure exactly where to put the gmapsupp.img file, I tried the root folder, then a sub folder called garmin but still I get no maps, do I require any additional files or folders on the card.

Any and all help much appreciated.

The dnx4230dab in my daughters car has a memory card in a slot inside the unit just under top cover have a look and see if you have one if can do that and let me know I may be able to help.