I installed mine with 3x20mm flat head screws and 4's of dowels. This way you only need a 4mm concrete drill and only have to "drill in" 20mm, which makes the whole thing much easier. Since the heads of my flat-head screws were a bit small, I added washers underneath. The 4mm dowels (Fischer) are designed for a maximum of 16kg in concrete, so they should hold without any problems.

It depends on where you mount the lamp. I had round-head screws, 5mm (with 6mm drill head) diameter and I think 40mm length with corresponding dowels. Just what is needed as standard.