It's a simple external torx socket available at any auto parts store. The size you need is an E8. The Volvo headlights are pathetically weak and adjusting the aim will do no good, if that is what you are trying to do.
E8?? Not sure about a Volvo but most vehicles today they are a Torx and T15 on headlights. You can get a single torx screwdriver or you can buy a set. They even sell them in sockets but those are more useful for like some calipers and stuff like that. I would buy yourself a multi-bit screwdriver set for the truck as most your dash screws are torx, tail lights are usually phillips head if not riveted. It's handy to have on a truck. I have a Husky set I bought at HomeDepot. Lowes sells the Kobalt brand which is good and of course Craftsman is decent enough for the truck. Almost any set will do. Auto Parts stores sell them, even truck stops but I hate their over priced cheap stuff. You can eyeball it but the proper method is in a shop manual diagram which you might find on the internet. You want to be so many feet like 5 or 10 feet from a wall and you measure two X's so high and so far apart to get it back to factory if they were tampered with. Like Dna said Volvo's are known for poor headlights. A lot has to do with the poor metal reflector shield inside the light housing and the lens discoloring.
My adjusting screws ends look like ends of torx screwdrivers. Its '07. What I look for is something like a socket.
Yes, it's a socket except for torx heads. Like was mentioned above, a simple inexpensive torx kit will include an E8 and others that you can throw in your tool kit for later.
If you don't have a torx I just used a socket, 7mm I believe. Raised it up about 10 half turns and it seemed to do the trick.
