Try this:
Click File - Import and Export - Export to a file - Comma Separated Values (Windows) - select Contacts - Choose a place to save the file - Finish.
Once the file has been saved onto the computer open it with Excel and see if all of your contacts are listed there. If they are, then import them back into Outlook. They should all show then. Also, if there are any sub folders under Contacts, export them as well.
If the exported list doesn't show all of your contacts, then you will have to go about moving them the long way. To do that you will need to go into the address book and view the list that is NOT showing up under the Contacts folder. Then one by one highlight them - click File - Add to Contacts. Doing this will move those contacts into the Contacts folder, and then they will all show under one.