Assemble Multiple independent project into a single group project

I have 3 projects which are at independent url on gitlab and are private project

I wish to add these 3 independent projects in a group project such that their relative URL become
http://gitlab.com/username/ultra-project/project-backend
http://gitlab.com/username/ultra-project/project-frontend
http://gitlab.com/username/ultra-project/project-auth

I have tried GitLab import but it is not allowing me to do so.
All these projects are from my same account and I wish to just group them together.

Have a look here.