How to change the setting on iMovie to produce the final video to an MP4 format?

I am having problems with the finished product of iMovie on my mac desktop. it comes out in a mov. format or QuickTime movie. Using iMovie on my MacBook pro, the same video comes out as a mp4 format orMPEG-4 movie.

The problem is I run the finished product through my Movavi Video suite 16 program on another computer ( an HP) to make a separate audio file and video file which I then upload to 4 different on line sites. I cannot use the mov. format with Movavi.

Is there a way to change the setting on iMovie to produce the final video to an mp4 format?

[Re-Titled by Moderator]