download this OST to Outlook PST Exporter Software that has ability to import OST to PST file format with all mailbox items like: emails, contact, calendars, inbox folders, sent items, draft, deleted folder items, journals, appointments etc. this software has a simple and easy user-friendly interface where both technical and Non technical user can easily access it without any technical knowledge.
Get more info- https://www.vsoftware.org/blog/how-to-split-ost-file.html
Convert OST to PST Manually
Open Outlook and go to the File menu.
Select the Import/Export option.
Choose Export to a file.
Select Outlook Data File (.pst)
Choose whether to export a specific folder or the whole account.
Check the Include subfolders box.
Next, select a destination for the Export, and then click Finish.