Team owners can archive a team when it’s no longer active, but is needed as a reference or they might want to reactivate it in the future. The team's conversations and files become read-only but can still be searched. Archive and restore teams using the Teams desktop app or Teams on the web.
Archive a team
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Select More list options 
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Select Your teams and channels 
to be taken to Your teams page..
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Under All, find the name of the team you want to archive, point to reveal, then select More options > Archive team 
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To prevent people from editing the content in the SharePoint site associated with the team, select Make the SharePoint site read-only for team members (team owners will still be able to edit this content).
Tip: Don't see these options? From Teams , select More channel options > Your teams and channels 
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To view and search through the content of an archived team, go the to the dropdown and select Archived Teams.
All of the team activity is frozen once the team is archived. No one will be able to start new conversations or reply to posts in a channel, add or remove channels, edit team settings, or add apps. As a team owner, you can still add or remove members, update roles, and delete, renew, or restore an archived team.
Restore a team
To restore an archived team, follow steps 1 and 2 above. Then, after selecting Archived Teams from the dropdown menu, find the name of the team you want to archive. Select More options > Restore team.