Most "stuff" that you put on your iPad is done though iTunes on your PC. So you need to get the movies in there and then sync the iPad. H264 is the normal format which iTunes supports, but you can play other types of movie file depending on the format and, sometimes, the app you use. There are several free (and paid) apps in the app store which allow you to play other file types.
If you give us a few more details about the movies you have at the moment (where they are, what format they are in, etc.), I'm sure folks will chip in with help so you can get them all on there and watched!