IPad users, how difficult is it to put movies on an iPad?

Going on a vacation with the g/f to Hawaii in January. We’re going to spend about a day on planes and in airports, so we’re taking some stuff to do/watch. I bought an external battery to keep some electronics stuff powered, and it specifically points out it can keep an iPad running and playing a movie for 10 hours (in addition to the iPad’s regular battery time). So I talked my brother into letting me borrow his iPad for the trip, as opposed to taking my own laptop or a portable DVD player (which woudln’t charge on the external battery, and would die too quickly to really be of much use).

The catch is I am not incredibly familiar with iPads. Save for situations such as this, I never saw the practicality in them and hence avoided them largely. My brother told me I would need to put any videos I wanted to put on it in the apple format (I’m assuming quicktime?) Does anyone know what that format is, a method to change the format of movies into that (like a convert x to DVD program if possible)?