image conversion plugin?

Hello,
Long shot, but curious if anyone has run across a plugin that will convert image file types on upload? or even something that will do the conversion once uploaded and in the media library or something… Specifically convert from .tiff to .jpg

The reason I’m asking is because I have a client who just can’t seem to figure out (after telling him many times) that his images should be in a .jpg format for them to show up in most browsers. I’m assuming he’s using a Mac so he sees them in Safari just fine. He keeps uploading .tiff’s then complains to me that people are complaining they can’t see the images… He’s very much a computer novice and really doesn’t understand the difference in file types. Just thought maybe if a plugin existed he could just keep doing what he’s been doing but the issue would be resolved as the file types would just convert without him knowing the difference..