Copy synced videos in/from Dailymotion
Go to the cache, and find the file that you want to play. There will be 2 files with the same name, one will be only a few kb, the other will be the video (should be a few MB).

Long press on the file until you get the menu. Then select "open as", then "video", then select a video player.

I used the stock one that comes with the phone even though I have several others I thought I would try that first, and it worked first time (this was on a Galaxy S3).

If they play then copy them where you want, pc etc. You might need to rename the video files (adding the .mp4 file extension).