This is a user forum, so no on here would know what your serial number is.
There is nothing that came with the CD? Did you not receive an email with the serial number (maybe in your spam box)? Nothing in your user account with Magix.com?
In boxed products the serial number is either on a label attached to the box or the paper cd envelope.
Do note that if you are on Windows 10 the program may have issues - it was only certified to run on Windows up to XP.
Given the age of the program it may not be registered on your Magix account at magix.com, you can try logging into your account there and selecting My Products to see.