Breeding millipedes?

hello guys , just got 30plus pcs of millipedes and i have seen some of them mating but i was just wondering , do they have gestation period and where do they lay their eggs?
my millipedes are the North American Millipedes , its color is the same as the redleg millipede but my millipede has a white feet.

I don't know about a gestation period, but they lay their eggs wrapped in little pellets of poo buried underground. So don't go digging around in the substrate, because you might destroy the eggs.

You just have to wait until you find babies. You will probably find them soon if conditions are right. I have a millipede of the same order (spiroboldia I believe, excuse the misspelling) and I have never found eggs although I often get young! The eggs do sit in the substrate for what seems to be a month or two before millipedes emerge.