Foreign vehicles all use metric measurement. So, the screw would be like 8mm or 10mm by 1.25 or 1.50.
Best to find another example screw from the door that fits in the hole that your missing. Or, take the whole regulator down to your local hardware store and they will size up the screw. My local ACE Hardware carries tons of replacement screws.
I'll bet it isn't. That might be the size socket or wrench you use, but that isn't how bolts are measured. I'm betting it's a 6mm also. Not sure of the pitch or length.