Transferring content can only be done with members that are part of the UF AGOL org. If both users are in the org and both users have had their role upgraded to Researcher or Student, then users can transfer content without the assistance of an administrator. See this Esri blog post for details. If you currently have the Publisher role, then you will need to contact GeoPlan to have your account upgraded. If the user that owns the content is no longer at the org, then you will need to contact GeoPlan and request the content be transferred by an admin.