Open Microsoft Teams and click the Teams section.

Click the cog icon in the top-right corner, then select Manage teams.

At the bottom of the next window, you will see an Archived section.  Click the arrow to the left of it to expand it.

Click the Team you want to access.

If you want to transfer any files to a new Team, click the files tab in the Team, then press the "Open in SharePoint" button.

In the window that opens, you can browse to any files/folders, select them and the press the "Copy to" button.

In the next window, choose the Team you want to move the files to.