That said, I can guide you through some general information and possible solutions:

: Check the inbox of the email address you used during purchase. Search for keywords like "VEGAS Pro 19," "Serial Number," or "Order Confirmation". Windows Registry (Advanced)

: Each key is tied to a specific user account. Sharing or using public lists of serial numbers is a violation of the software's license agreement and often fails because the key must be registered to a MAGIX account during activation. Boris FX Forum How to Find Your Legitimate Serial Number