Hi Subhash,
The fastest way to get a transcript is to upload the same .mp4 to Word for the web and use Transcribe.
Open a new Word document in your browser, select Home > Dictate > Transcribe, choose Upload audio, pick your .mp4, then let it process. When the transcript appears in the right pane, select Add all to document to drop the full text into your file and save or copy it wherever you need.
Word for the web accepts
.mp4uploads, has a monthly limit for uploaded audio of 300 minutes per user unless you have a Copilot license, and individual uploads must be under roughly 200 MB.
If you try this now, do you get your transcript within the time you need?