[azazel1024]

Advanced auto or similar. Look in their miscellaneous parts section, they aren't in bolts. You want the retainer clips and then bolts to fit them. Almost all of my retainer clips have broken because of Mazda's cheapness. I don't recall the exact name of them, but you'll see what it is you need. They are U-clips or something similar where they clip over the splash shield and then the bolt goes up through them.

Unlike Mazda's cheapness with their welded nut on clip, these are machined from a single piece so they aren't going to break over time.

As for the bolts, yes it does matter. The first part is the pitch (1 thread per mm, 1.25 threads per milimeter) the next is the length. It is probably something similar to a 10mm-1.25x20mm bolt. I'd suggest just replacing all of the clips now if they aren't broken yet, they will be and they are a HORRIBLE pain to get the spalsh shield off once they break.
-Matt