I need help moving ,dbx Outlook Express messages to Outlook 2007.

I backed my old email Outlook Express .dbx files to a USB drive. How do I
import my mail messages and sent files into Outlook 2007? When I try to
use the Outlook 2007 Import wizard, chose other files and then chose Outlook
Express 4.x, 5.x, 6.x and internet mail--- and then browse to the folder
they are in I get an error message that there are no internet email
messages.

Thanks

Robert