No problem. You're not the first to ask. It seems like an obviouls setup on the surface, but it's just not there.
Some people have gone to considerable trouble to get their DVD movies on the iPad, and succeded, but it requries ripping them to a digial format, setting up a server, and streaming them to the iPad. Doable, but probably more trouble than it is worth if you don't already love tinkering with computers and stuff. Or want your DVD collection on your iPad very very badly.