Calendar in Public Folders to move to Office 365

I have moved my mailboxes to Office 365 but have a calendar in a public folder on my old exchange 2003 server. I need to move it/ copy it to a shared mailbox in Office 365 so that all staff can access it.

I can access it via IIS on the Exchange server but not in any other way.

I had thought of moving a mailbox back onsite but not sure how to do this

or setting up an onsite mailbox for a new user but I get an error saying name is not in contact list.

Please help

Diana