Hi Priyanka,
Are you using a 3rd party plugin or Moodle's standard multimedia filters? Moodle's multimedia filters should generate the correct embed code from whichever video file format you're using. There's no need to convert video files from one format to another, which is a lossy process and degrades the quality of the video.
Firstly, I'd ensure that the multimedia filters are enabled and correctly configured in the site administrator settings.