Assets migrating doesn't work..

To be more concrete - I simply copy/paste all the needed folders to my new project and it doesn’t see them - why??
Thanks for helping!!

Just copy and pasting the folders isn’t going to work. You need to open up your source project, right click on the folder/asset, choose Export, and then select the Target Project.

But, I do have examples with some source projects, where it works just fine!! So, what’s the difference?!