Which screw and anchor should I use to mount a projector screen?
The screw should penetrate at least 1", more if possible into the material (concrete, brick, etc.).  So if you have 24mm thick wood, and you want the screw to hit a depth of  say 1.25" inch, you need ~24mm+32mm (1.25") +2mm (exposed screw) = 64mm (2 1/2") screws.

Now you need a plug or anchor that can accept this length of screw. As for size of screw, I'd use a #6 or #8 screw.

Another (easier IMO) option is to use a concrete screw that does not require an anchor - they are sometimes known as Tapcon's (common North American brand).

Make sure to drill the hole at least 1/4 deeper then needed.