I can't work out which notes are actually played in these mordents, it seems (from the specified fingering) to include more notes than in a typical mordent?
The terminology for baroque ornaments in different languages is very confusing, but "pralltriller" would be a better name for these than "mordent" IMO.
Be that as it may, following the interpretation suggested by the fingering, the notes are Bb Ab Bb Ab for the first one and C Bb C Bb for the second.
The first note goes on the beat, not before it, and the first three notes should be as fast as possible. CPE Bach in "The true art of playing keyboard instruments" says that this is the only type of ornament which can not be demonstrated slowly to beginners, and that it must "really prallen" - i.e. "crackle".
The bad news is that they are easier to play, and more effective, on a harpsichord than on the piano, where the heavier key touch and lack of the "plucked" attack of the harpsichord means they have to be played slower - which kills the "crackling" effect. On a piano, at a reasonably brisk tempo, you might be better off omitting them altogether.
Actually, it's quite hard to find a video on YouTube where a harpsichordist plays these ornaments, but here's one: