Yes, the official document provided above by michev has given detailed information about your question. This related thraed discussed about the similar topic like yours: How to Check/Verify Effective Retention Policy on Non-Message Folders
Open the mailbox with MFCMapi, then open the store and drill down to the folder you wish to check (it's under the Top of Information Store node). In the property list of the folder, check the PR_RETENTION_PERIOD setting - if the property doesn't exist, there is no policy applied. However, in your case, the root (Top of Information Store) should have a policy, which should trickle down to its subfolders unless another tag is present
In addition, you may also use powershell to check what policy is applied to the user:
Get-Mailbox user | Select RetentionPolicy
And the tags added to the policy
(Get-RetentionPolicy "Policy").RetentionPolicyTagLinks | Format-Table name
The official document here introduces about Retention tags and retention policies for your reference as well
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