What do I feed it? Special sub? Moist? Dry? Hide?
There is a millipede care sheet stickied at the top of the myriapod subforum. They should generally have moist, but not wet, substrate and lots of leaf litter and decaying wood to feed on. You can supplement them with fresh fruits and vegetables (organic). greenhouse millipedes are extremely hardy and present pretty much globally because they have been introduced beyond their native range and are highly adaptable. All you would really need is a container that will hold humidity (like a Rubbermaid container), a substrate rich with rotting wood/leaves, and an occasional misting with distilled water.