|The dbx files are your Outlook Express boxes, such as Inbox, Outbox, Sent Items, etc.|
They are only any use to you if you want to overwrite Outlook Express files on a computer that has just had a new install of Outlook Express. Even then it is not the official way of migrating emails. They are incompatible with Outlook, particularly modern cloud based versions.
Follow the link given by trvlr at #1.
Always pop back and let us know the outcome - thanks