In order to properly migrate Public Folders, admin credentials are required for both the Source and the Destination.
Specifically:
At the Source: Read-only access to all Public Folders is required.
At the Destination:
- Admin privileges are required for the migrating "admin" account so that all fields can be set at the Destination.
- Ownership of Public Folders are required on the Destination so that new subfolders can be created.
For further details, read this article about creating an administrator account for login.
Note: Once you have created an account with administrative credentials, you will also need to set full permissions for Public Folders explicitly for the administrator.