Mass update Case Created By User and Case Record Create Date

Hi All,

Does anyone know how you can mass update the Case Created By User and Case Record Create Date fields? I have just imported a few thousand Cases but these fields auto populated with todays date and the user who run the import. As they are not fields you can map to I have tried:

(1) Exporting a Case group - Updating the fields and then reimporting

(2) On Demand Workflow

(3) Flow

I gather the issue I'm having is these are system fields which are read-only. Is there a way to update these type of fields? I have no coding experience so preferably a way through a functional change/update 

Thanks.