convert .mov video to .mp4 with ffmpeg
To convert videos, I like to use handbrake. You can find it here: https://handbrake.fr/ I use it on Linux but it should work well on MAC too.
For HandBrake:
handbrakecli -i {in-video}.mov -e x264 -E facc -o {out-video}.mp4
For ffmpeg:
ffmpeg -i {in-video}.mov -vcodec h264 -acodec aac {out-video}.mp4