Open Outlook and go to File > Open & Export > Import/Export. Choose Import from another program or file and select Outlook Data File (.pst). Browse to the PST file location and select the desired options for duplicates. Use Microsoft Outlook: Open Outlook on your computer, and add your Office 365 account if its not already set up. . https://www.vartikasoftware.com/product/vs-pst-to-office365-converter.html