Converting swf to inferior video is a sin but in this case it's just a video embedded inside a swf so I guess it should be okay.
You should be able to extract the video using JPEXS Free Flash Decompiler. If that fails you could try Swivel by Newgrounds, which basically records a video while you view the swf file.
for flashes that are just a video file, you can actually change the extension to .flv of course some software might check the headers so this isn't the best solution.