I think you already have all the bits required to fix this, as you say you have 18 .dbx folders.
Try this:
Copy the Folders and Sent items .dbx folders to your Desktop. The Folders.dbx file ensures that OE recognizes the data when you import the data.
Start Outlook Express, click Import on the File menu, and then click Messages to start the Import Wizard.
In the Select Program dialog box, click Outlook Express as the e-mail program from which to import, and then click Next.
In the next dialog box, click Import mail from an OE store directory, (which in this case will be your desktop) and then click OK.
Locate the temporary location of the .dbx files on your Desktop, and then select the 2 files (Folders and Sent) that you want to import. (Hold down Left mouse button and drag over the 2 files to select both files). Outlook Express should begin to import the old mail and to create or to populate folders.
Make a note of how that goes and let us know.