Hi Michael Scofield,
Thanks for the update. If you don’t want to use this manual procedure and are looking for a third party utility then I will recommend advanced MS Outlook PST merge software on behalf of my personal experience. By using this tool, you can easily combine multiple PST files easily. This tool provides effective features to merge multiple PST files like; Merge PST file, Join PST file, and merge contacts folders. You can also remove the duplicate items during the merge PST file process. I hope it will work for you.
Thanks & regards
Barry Alllen