Just Follow the Below Steps
OST to PST migration can be done easily
You can Export mailbox as a PST file
Login to Outlook with the Exchange account that was used to create the OST files. And to export the OST mailboxes to PST, follow the simple procedure:
Go to Files >Open & Export and click Import & Export.
Select Export to a file; then click Next.
Select the second option—Outlook Data File (.pst)—and click Next.
Select the folder which you want to export and click Next.
Browse the location where you want to save the new PST file and choose the options regarding the duplicate items.
Note: There is an optional choice to provide a password to the PST file, but you can easily move ahead without choosing it.
Before that make sure you learn enough about email migration
Hope This will Help You,
Edit by iMacg3: Removed external link
Edited by iMacg3, 12 October 2019 - 08:57 AM.