when I go to the personalization section, and then click into the "Window Colour and Appearance",it is automatically appeared in a classic window style, How can I change it to a modern style? P.S. This is the only one that appeared as classic style in my computer, the other ones are fine."

No, it doesn't work either, it goes back to the same classic window

On this page go to TOOLS > FOLDER OPTIONS > GENERAL tab > and look whether Classic Folders is checked under "Tasks"