how do I convert an mp4 to mov on a mac

QuickTime does it with nothing extra to install. Open the mp4 in QuickTime Player, then File > Export As and pick a resolution. What it saves is a .mov. It re-encodes the video though, so a long clip takes a while. If you're comfortable with the terminal and have ffmpeg, ffmpeg -i input.mp4 -c copy output.mov just swaps the container without touching the video, done in seconds.