You have a project for your App Engine application that serves a development environment.

Use gcloud to create the new project, and then deploy your application to the new project.

Use gcloud to create the new project and to copy the deployed application to the new project.

Create a Deployment Manager configuration file that copies the current App Engine deployment into a new project.

Deploy your application again using gcloud and specify the project parameter with the new project name to create the new project.