Look in the trunk
The position light bulbs are located in the back of the vehicle. There are several bulbs for each location, so it is not easy to find the burned out bulbs without actually pulling the lighting assembly out and inspecting the bulbs.
Open then trunk and there should be access panels on either side of the trunk opening.
Open the access panel and you will have to pinch plastic holders to remove the lighting assemblies. There are several on each side.
One of the bulbs is burned out in one of those assemblies