The front and back door motors are different as are the driver side and passenger side motors different. (4 different motors) You have the right ones in mind for the rear driver side door but you need the manufacturing date of your car which can be found on a sticker inside the driver side door door jam. This sticker has tire pressure information and other stuff, including the manufacturing date of your car. Those two part numbers have been superseded (updated) by Infinity Part Deal. The 80731-JK00B is now 80731-JK00C for your car if built between 10/01/08 and 11/01/09, according to Infinity dealership websites I just checked. The dealership sites do not even recognize the other part number so something is a bit strange here with the Infinity Parts Deal website I linked you to. If you visit the website https://www.infinitipartsdeal.com/
or a dealership website like https://www.infinitipartsdeal.com/
and enter the VIN number of your car, you will get the best identification results for parts to your car. You can always call a parts department at any dealership to confirm the part number as well.