Formula question about the Bridge and full wave rectifier,where are these number from?
The ripple can be approximated by a sawtooth. The ratio of peak to RMS of a sawtooth (proof involves a bit of calculus and is left as an exercise) of a sawtooth is Vr(pp)/(2\$\sqrt{3})\$. Keep in mind that the ripple goes plus Vr/2 and minus Vr/2 so you need only integrate one half of the triangle. 
If you assume a constant current from the load and the period of a half cycle, and the above formula you get a constant of 2.41 milliseconds. That should give you a hint of what units to use for C.