I have re-installed Sonar on a brand new machine. I do not have a serial number for DPro. And there is nothing on my product information page where the Sonar codes are. Suggestions?

It should be listed in your user account under "my products." Support -> my account -> my products.
 
Rocky

Dim Pro should be listed with your other products in your account.  You will need both the serial and registration code to activate it.
 
If it was never listed in your account, it may be associated with an old email address.  Cakewalk used to have a customer service contact for account issues, that was able to easily resolve this type of issue.  Hopefully they still have the lights on...
 
I had several products missing from my account a couple years ago, and they were quick to update everything when I provided purchase details, and the old email address I was using when I  purchased the products.

It is not on my product page. Dimension pro is listed. That's where I downloaded it again from. But there are no serial numbers. And I have never used another email address.

Do you have Cakewalk Command Center installed?  I have a copy of Dimension Pro listed there, along with the serial and reg code.  https://www.cakewalk.com/Command-Center
 
If not, just install it and login in with your user ID, then take a look in there.
 
If nothing there, all I can suggest is to shoot customer service an email.
>>> https://www.cakewalk.com/Support/Email/Activation