think two are just pop in press studs, third one might be a small screw, don't know if they can be re-used or if they will be as secure again, some people used self tappers. I (garage) used what what was supplied but I have also added double sided sticky pads to keep them flusher. Have a look at my pics under the One Stop Modifications for pictures of my mudflaps and see if same fixings as yours, torqsteer website might have pics of the brackets and fixings too.
Glad I can be of use on my lunch break
, it's nice out so popping out for a walk, in a moment
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SW