Converting videos?

Hello everyone.

I really need help with this because I'm at a complete loss; let me explain. I airdropped a video from my phone to my Mac so I could mess around with iMovie. When I tried opening it in iMovie, I found out that .mov is no longer compatible and that I need to convert the video. So I consulted this guide by Apple on how to convert a video in Quicktime:

However, after I select the resolution I want, it just asks me where to save the video, not letting me change the video type. So then, I learned you can convert videos with good ol VLC So I downloaded VLC, selected my video and conversion settings, and then I can't save the file. Whenever I select the directory I want and press save, it closes and brings up another save button, which just opens up the save location; it's just an endless loop. I've also confirmed this is not a Voiceover issue, just in case.

So there you have it folks, I just want to open a video in iMovie. I'm not sure if it's me or MacOS, but any help would really be appreciated.