One of the best free method to convert MBOX to PST files is to use the eSoftTools MBOX Converter tool. It will convert individual or bulk MBOX to Outlook. MS Outlook 2019, 2016, 2013, 2010, 2007, and 2003 will access the updated MBOX PST file since it is in Unicode format. It can also have free trial variants. Using this software is the best way to keep your mail resources, attachments, addresses, and other mail-related things safe. It's supports all windows and Outlook versions up to 10.
For more info- Convert MBOX to PST files
For more info- Convert MBOX to PST files