@slowtrk-radyo You're not changing the format as such, you're not changing anything within the file, you're simply giving it a file extension that at the moment it doesn't have. You're giving it an identity, like giving it a name..
Try changing it to .mov or .mp3 or .avi or .mpeg etc, there's a long list of choices & see if it also loads into Vegas. RogerS suggested mp4 because it was the most likely to work, the commonest container choice & until you find out the correct extension that's what you'll have to accept.
<.raw> is another extension to try. That has worked for me a few times when files would not open in Sound Forge otherwise.. though .MP4 or .M4u should work if it is an AAC audio file.