Converting m4a file to mp3 from iPhone

[Solografer]

Trying to convert m4a file to mp3 sent to my email from iPhone, but VLC says output file already exists and will get overwritten if I continue. Even when I click Overwrite, no data results. Suggestions? Upon closer inspection, an m4a file is actually designated as a VLC app file, which could have something to do with it. Hmmm....