There are a lot of free video file converters out there. Format factory is one that I've used. Just Google 'video file converters' and you'll find a lot of them. I had some success with Format Factory, but still had difficulties using converted versions of 'newer' formats in Sony Vegas. I tried a number of the free conveter programs before simply breaking down and buying a new version of Sony Vegas.
You can get Movie Studio Platinum 12 for less than $50. No need to get the Pro version unless you're really doing something on the professional level. I've used Movie Studio for both home use and for developing safety and handling videos at my place of employment. The safety and handling videos are well over an hour long and are relatively complex (several video layers, screen text, sound track, narration track, video, stills, screen captures, etc. etc.), but I still did them with the Movie Studio version of Vegas. The older version I originally used limited the video tracks and sound tracks to three each (if I recall correctly). The newer version allows many more. There are tons of effects - many of which I haven't even bothered to try and really didn't even need. But, you can do some really terrific effects, if you must or are so motivated, at a budget price.