Linux doesn’t use file extensions; rather, the file’s type is part of the file name. To find out the true file type use the file command.

How do I get the file extension to show?

In Windows Explorer, choose Tools > Folder Options. Click the View tab in the Folder Options dialog box. In Advanced Settings, select Show Hidden Files and Folders. Deselect Hide Extensions for Known File Types.

How do I show file extensions in Ubuntu?

There is an option for it to show extension. There is no such thing as a file extension on linux systems. File extensions are simply part of the file name, and they’re not hidden by Nautilus, and extension type is determined by the file header.