Hi Rosemary and welcome,
The email that you received contains an attachment which is your reg key.
It sounds like you understand this...I have no idea why you can't locate the attachment unless it is being blocked by your email server or a filter on your end. If this is the case however, you shouldn't have received the email at all.
You can request that the reg key be sent again. The process is automatic and takes only seconds depending upon your connection.
Click on this link:
Be certain you use the same email address that you used for the purchase
and also make sure that you have DVDFab 5.x in the dropdown.
Hope this helps and let us know