You can use the CloudMigration PST converter software. It is an excellent and affordable tool for converting Outlook PST files to MBOX files. It can make conversions into multiple file formats, including EML, MBOX, PDF, EMLX, HTML, MSG, VCF, and other file formats. It allows users to migrate Outlook PST data into Gmail, Yahoo, Opera Mail, Thunderbird, IMAP, Hotmail, etc. Installation of Microsoft Outlook on your PC is not required. The full mailbox folders, subfolders, and attachments can be previewed, and PST files can be imported into Google Workspace. It works so well with all the versions of the Windows.