You'll need to find-out first which infotainment system you have - e.g. Audio20 or COMAND NTG4.
If you're not sure, run the VIN through a free online VIN decoder to see what options have been fitted to the car.
Alternatively, if you post your VIN here, someone with access to EPC will confirm the correct part Number for your car.
Also, if you are planning on replacing it yourself, then once you get the old unit out, it will have a part number - and that's what you'll need to get off eBay or Amazon.