Many of the techniques that American filmmakers use actually came from progressive French filmmakers. Many classic films that shaped film history are French, but that does not mean that you need to miss them just because you do not speak French. Converting the spoken words from the movie is not actually possible, but obtaining an audio track of dubbed English or English subtitles is. Finding a dubbed English version takes a simple online search.
Go to a website like Opensubtitles.org, which has a large database of English subtitles (see References).
Find the correct movie and download the English subtitle file.
Using a program like DivX or VLC Media Player (see References) you can watch the French movie with English subtitles. In "Preferences," under "Audio Preferences," select the English subtitle file for use.