How to reimport missing files?

Hello, I’m very new to unreal engine and today after I pressed the button to save all the changes, i got a bluescreen (never happened before, at all, not only in ue5). Once i reopen the project i’m missing some blueprints including the character.
The files are in the content folder


but not in the project folder

i tried to copy paste them but it says the extension is not allowed