Close and save anything that you are working on before proceeding. The next steps will involve killing explorer and restarting the PC.
Open a command prompt.
Copy and paste each command below one at a time into the command prompt, and press Enter after each command.
If the icons are still not displaying properly after rebuilding the icon cache, then download and merge the .reg file for the .ico (ICO) option here to restore the default associations of .ico (icon) files in Windows 10.
taskkill /IM explorer.exe /F
DEL /A /Q "%localappdata%\IconCache.db"
DEL /A /F /Q "%localappdata%\Microsoft\Windows\Explorer\iconcache*"
shutdown /r /f /t 00