They are M6x1.00 not sure of the length though, maybe 15mm?
But I have a suggestion for you. Before using the screws to secure it, have a look at a DIY I did a few years ago when I installed my Valenti light.
https://www.ft86club.com/forums/show...hlight=birdtrd
I removed the push nuts that the screws go into and used plastic body push pins instead. The bolts and push nuts get rusted together then the plastic ears break when you try to remove it...now you have nothing to secure it to the bumper.