If the circles really are paths, then you can just select them and then pick a "fill" color. Use the palette at the bottom of the window or the fill/stroke controls (ctrl-shift-F).
edit oh wait - if they're "holes" in a bigger path, then you can try this. First, make a copy of the outer shape (the thing with holes). Make a random shape (rectangle or whatever) that's a little bigger than the hole, and make it a path (object to path). Drop the copy of the original shape over your rectangle, make sure both the shape and the rectangle are selected, and then do a "Difference". That should leave you with a complete path that's just the "hole".
edit oh wait - if they're "holes" in a bigger path, then you can try this. First, make a copy of the outer shape (the thing with holes). Make a random shape (rectangle or whatever) that's a little bigger than the hole, and make it a path (object to path). Drop the copy of the original shape over your rectangle, make sure both the shape and the rectangle are selected, and then do a "Difference". That should leave you with a complete path that's just the "hole".