See explanation below
Explanation:
From the Microsoft 365 compliance center, select Policies > Retention.
Select New retention policy to start the Create retention policy configuration, and name your new retention policy.
For the Choose the type of retention policy to create page, select Static. Adaptive policies don't support the locations for Exchange public folders or Skype for Business.
Depending on your selected scope:
- On the Choose locations page, toggle on or off any of the locations except the locations for Teams and Yammer. For each location, you can leave it at the default to apply the policy to the entire location.
Information specific to locations:
- Exchange email and Exchange public folders
- SharePoint sites and OneDrive accounts
- Microsoft 365 Groups
- Skype for Business
For Decide if you want to retain content, delete it, or both page, specify the configuration options for retaining and deleting content.
You can create a retention policy that just retains content without deleting, retains and then deletes after a specified period of time, or just deletes content after a specified period of time.
Complete the configuration and save your settings.
Reference:
https://docs.microsoft.com/en-us/microsoft-365/compliance/retention?view=o365-worldwide
https://docs.microsoft.com/en-us/microsoft-365/compliance/create-retention-policies?view=o365-worldwide