those sticky pads around the holes are to seal the screws,put some silicon around the holes,locate your plate and fix to car,
when i had a mercedes i had water in the boot wheel well,mercedes found the water had been
spiraling around the screw threads of the number plate screws and then dripped into the boot giving me a pool of water.
the leak was a right bugger to find,it was only when the pressure washer came into force did they find it.