You can use Import
directly as follows:
Import["MVI_9855-183.mp4", {"AVI", "ImageList", Range[1, 110, 20]}]
This will import one frame every 20, between the first and 100th, and return them as a list of pictures.

As you can see above, at least in the case of the mp4 files I have at hand I was able to "convince" Mathematica to import them directly by specifying the AVI format for the file. I am no expert in video file format, however, so I can't claim that I understand why that worked, or whether it will work for you as well.
If you are on Windows, you may also be interested in Simon Woods's MathMF package that carried out video input output functions using Windows Media Foundation. See it described in his answer to this question: Importing videos in Mathematica