There have been a number of other posts on this Forum from members trying to do more-or-less what you are advocating with varying degrees of success. The general concencus seems to be that iMovie will only (easily) work with the iPad2's built-in camera. To be able to import movies from other cameras requires some fairly precise and protracted re-formatting. If you only want to be able to view the movie then a third-party app, such as oPlayer, might be an easier route.
If you really want to be able to import it into iMovie and don't mind reformatting the file on your PC/Mac then I can point you to the thread that discussed this.
Tim
Scotland