JPEG and JPG are exactly the same image formats. There is no technical difference between a .jpg file and a .jpeg file — they both use the very same JPEG compression algorithm and store image data in the exact same format.
The difference is only in the suffix, being a legacy issue from the early days of computing. JPEG was created in 1992 by the Joint Photographic Experts Group. When Microsoft released early versions of Windows, the OS had a constraint: file extensions had to be no more than 3 characters.
This forced the 4-character .jpeg extension to be shortened to .jpg for Windows computers. Apple and Unix platforms, which never had the three-character restriction, continued using the complete .jpeg file extension from the start.
Even though both extensions work identically in almost every modern software, some more info situations in which a platform might need the .jpeg extension. For these situations, changing the extension from .jpg to .jpeg is sufficient.
No image data conversion is necessary — simply updating the file extension fixes the compatibility concern usually.
Use alljpgconverters.com offering a totally free browser-based JPG to JPEG tool requiring no software needed.