1. Convert through EML Files
This solution involves the idea of saving the required MBOX emails to EML file format and then exporting these files to Outlook application using Import/Export feature. Let us know this sequential stage wise process as described below.
Create a New folder & move MBOX file items
First, open the MBOX email client and right-click on any mailbox folder. Select the option New Folder, provide a name to it and select Create Folder to create it. Now copy and paste or drag/drop desired MBOX emails (for conversion) to this new folder.
Convert to EML format
Select all the MBOX files for conversion in that folder and right-click on it. Choose the Save as to EML option. Provide the path location to save the converted EML files.
Move EML to Outlook EML files
Open the Outlook EML file folder and drag-drop the earlier saved EML files to it.
Export EML files to Outlook PST files
Open Import and Export wizard in Outlook by following File>Import >Import/Export.
Then select Export to a file option and click Next.
Select Outlook data file (.pst) as the next option and click on Next.
Now, from the folders, select that folder with EML files and click on Next.
Add the saving location for PST file and click on Finish.
The MBOX file is converted to PST finally.
I hope these steps will be useful to convert MBOX to PST manually.