Can you try a video editing software trial at all? Download something like a 7 day trial of Adobe Premier Pro go to the video suite with whichever file you want to convert load it in and then do an export as they've got a load of different file type options?
Might need a bit more detail about what you're trying to achieve? What format are you looking to go from/to etc?
The free version of DaVinci Resolve is incredible and relatively easy to use with the aid of bit of YouTube tutorials etc. You only need a standard mouse/keyboard to use it not a whole full on editing suite like some of their photos show.
I've used Adobe Premiere and Sony Vegas in the past and this seems very up there. I'm not a pro, I've just used them to cut-up a few videos with transitions etc.