Some MPEG-1 videos use dat extension which can get confusing, as this extension is used by many file types. In case that you are looking for a way to convert Apple QuickTime videos (.mov) to MPEG-1 .dat files, you have to use one of the dedicated video conversion utilities that support both of these formats.
Open MOV file Open DAT fileA video converting tool for macOS / OS X
A video converting tool
Universal All Purpose Free Media, Audio & Video Converter Player Recorder