We would know nothing about yahoo mail. Look at Outlook's import Wizard to
learn what file types you can import. Then you can figure out what file type
yahoo mail is or what tile type you can create from it.

If you're speaking of the contacts you have stored in the Addresses folder
on the Yahoo! Mail website, it's fairly easy.  Open the Addresses page, then
look in the upper right corner.  You'll see "Sync", "Import/Export",
"Options".  Click "Import/Export".  On the lower half of the page, click the
"Export Now" button just to the right of the label "Microsoft Outlook".  It
will create a CSV file you can import into Outlook.