It's been a while since I worked with ".mov" files, but I remember them well. I had Windows 98 that came with MediaPlayer. I also installed QuickTime and RealPlayer. Every time I updated one or another some "file associations" would be hijacked to whatever had been last updated. It was very frustrating until I figured out what was happening.
Anyway, at the time, the different apps had ways to "save as / export as" from one format to others. IIRC I needed to install a few codecs and experiment with different rates before I had what I considered to be success.
Things have much changed since those days, but I would first check to see if your app has the "save/export" features you need.
If not you might try a third party converter, but beware such apps are notorious for being malware vectors so if possible go with reputable vendor even if it's only a trial or paid.
The other option is to upload your files to a CDN cloud server that does the converting for you.
Or as spaceshiptrooper suggested, find a site that will do the converting.