Is there a simple way to convert .jpe images to .jpg format?
You can certainly convert JPE images directly to JPG images (.jpe to .jpg conversion), it would, however be quite pointless, since both file types are essentially JPEG Images using different suffixes.
If really needed, simply rename your file's JPE suffix to JPG.
Regardless of that, you can obviously use numerous available graphics editing programs or (online) conversion tools capable of converting JPE to JPG.
A bitmap graphics editing program
Raster graphics and 3D computer graphics application, which is a refresh of Microsoft Paint.
A basic Apple MacOS document and image viewer
A popular utility for viewing and converting graphic files