Backing up Outlook

When I got my Passport, it had software on it to back-up Outlook emails.  I deleted it, foolishly, thinking I would not need it and could use the space for other digital storage.

Now I am getting rid of my old desktop computer and need to back up my Outlook emails but can’t seem to find anything on the WD website that indicates what I need to download (or restore) to do so.

Anyone able to shed any light on this?  I recall getting a message when I deleted the Outlook back-up software that it could be restored or re-installed but have no recollection what it was.