Since no one has responded yet: First of all, they're assymetrically-spaced: The pair of holes on one side is closer to the centerline of the wheel than the pair on the other side.
The holes need to be big enough to allow 6mm machine screws to fit through, and from experience, you'll probably need a bit of "slop".
With the wheel sitting in front of you, looking at the surface you plan to drill into, the holes on the right-hand side are closer to the centerline.
Distance between the front and rear pairs of holes: 3 cm
Total horizontal distance between the left and right pairs of holes: 17 cm
Horizontal distance between the left pair of holes and the centerline: 9 cm
Horizontal distance between the right pair of holes and the centerline: 8 cm
Your mileage may vary...
_Dave_