As a quick, secured and affordable solution, I would suggest you Office 365 Backup to pst converter software
which allow the users to easily backup of office 365/Exchange mailboxes to PST & Restore them. This tool enable user to backup of multiple Office 365 to PST file in just single go. With this tool user can easily restore the PST files to Office365 and exchange server. this also import the PST to Office 365 in just few clicks. all users both technical or non technical can easily use this tool without any technical knowledge rather basic computer skilled person is also easily use this tool and convert office 365 to outlook pst.