Hello and welcome to the user to user forums so there is no-one here that is a Magix staff member to help you.
You should have had an email receipt with the activation code within it when you bought the program from the Magix website. If you did not receive such an email then first check your spam folder for it.
If the email has been deleted or blocked then try contacting Magix at infoservice@magix.net with details of your purchase.
If you bought the program from a third party website or shop you must take your problem up with that vendor as Magix would have no record of the transaction and be unable to help.