How to Archiving repositories in GitHub

We recommend that you close all issues and pull requests, as well as update the README file and description, before you archive a repository.

Archiving a repository

1. On GitHub.com, navigate to the main page of the repository.

2. Under your repository name, click  Settings. If you cannot see the “Settings” tab, select the  dropdown menu, then click Settings.

3. Under “Danger Zone”, click Archive this repository

4. Read the warnings.

5. In the text field, type the name of the repository you want to archive.

6. Click I understand the consequences, archive this repository.

Unarchiving a repository

1. On GitHub.com, navigate to the main page of the repository.

2.Under your repository name, click  Settings. If you cannot see the “Settings” tab, select the  dropdown menu, then click Settings.

3. In the “Danger Zone” section, click Unarchive this repository

4. Read the warnings.

5. In the text box, type the name of the repository you want to unarchive.

6. Click I understand the consequences, unarchive this repository.

Ref: https://docs.github.com/en/repositories/archiving-a-github-repository/archiving-repositories