Well, it depends on the resolution and the length of the films you are planning to keep on the drive. Let me give you an average estimate.
On average, a 1080p movie lasting 2 hours is around 7gbs. So on your drive you could fit about 106.
At 720p for a movie lasting 2 hours the average is 3.5-5gbs. So it would hold about 150 - 214 movies.
These are the most common resolutions, if your goal is to fit as many as you can, reducing quality is always an option to allow space for more.
Hope this helps!
