You can export an OST file to a PST file in Outlook by following these steps:
Open Outlook: Launch Outlook on your computer.
Create a new PST file: Create a new PST file by going to File > Account Settings > Account Settings. Select the "Data Files" tab and click "Add." Choose "Outlook Data File (.pst)" as the type and select a location to save the PST file.
Import the OST file: Go to File > Open & Export > Import/Export. Select "Export to a file" and click "Next." Choose "Outlook Data File (.pst)" as the export type and select the newly created PST file as the destination. Choose the folders you want to export from the OST file and click "Finish."
Wait for the export process to complete: Depending on the size of the OST file, the export process may take some time to complete.
Access the exported data: Once the export process is complete, you can access the exported data in the new PST file.
Greetings,
Peter