I have a 2015 XC60 R Design, and I can confirm the wiring for the Ground Lights (that’s what Volvo calls them) is present and is operational. Also, the wiring for the Door Pocket lamps is also present and operational. Here’s where they are
The lamp units for the Ground lights are identical to the Footwell lights and the Tailgate light. The Volvo part number is 1286317. If you want a guaranteed easy fitting this is probably what you want. They cost around £30 for a pair from Volvo. However, I think the light output is very poor and I don’t like the warm white colour (I’ve replaced my boot and footwell lamps also).
I went for aftermarket White LED units from ebay (Just search the above part no. for loads of options). Although the performance is exactly what I wanted (very bright and white), the dimensions of the fitting were poor and required filing of the lamp housing and connector socket, and wedging the connector in place on the lamp to get a secure fit. For me it was worth the effort for the light output.
For the Door pocket lights I just used generic LEDs with diffusers, wired in to the original plug.