You can see all your archived projects in the sections they were in, in dimmed color once you enable the “Show Archived Projects” option in the sort dropdown:
You can activate an archived project if you're an Editor or higher in your workspace. Hover over the project and select “Activate Project” under the Settings menu:
☝️ If you’re on the deprecated Starter or Growing Business plans, the Admin or Owner of the project can activate them.
Keywords: unarchive, re-activate