Hi Guys ! I deleted my materials folder by mistake 
Fortunately I had a copy of the backup project, so I transferred a second time the material folder inside the project, instantly Unity relocated the materials apparently seems quite correct, you can confirm that I have done well? I have to do other things to be sure that everything is back to normal?
Thank you 
When you delete anything, it goes into your Windows trashcan; Just go there and restore the files (they usually go in pairs with .meta files, which must be restored as well
The project panel (with folders) is in fact a direct representation of Windows Explorer (the one you will see if you press “Windows+E”), and you can get there by “right-clicking —> Show in Explorer”