To restore them to their original form, you need to change the application registered to open .url files.
- open the Settings Windows 10 (keyboard shortcut + [ I ])
- choose Apps > Default apps
- at the bottom you will find the Choose default applications by file type command; locate the .url extension
- click the Firefox icon and choose Internet Browser
- a general Internet browser should be registered with the .url extension before closing the window
When you close the window, the icons on the desktop will be “fixed”.