First - please never post personal information eg email address etc or serial numbers, invoice numbers etc. If members of the forum wish to contact you they can contact you by Private Message (PM).
If you previously registered the software you can retrieve your serial number by going to the Magix website - magix.com.
Top right of the page you will see a link My Account
Click this link and login with the username and password you use.
Once logged in on the left you will see a link to My Products, click this you should then see your registered product(s) and serial number(s)