A unique string (usually starting with 1TR) provided at the time of purchase.
Are you having trouble with a during the activation process, or
The Sony Vegas Pro 13 authentication code is a after a serial number is entered, though it was often optional for users who activated their software online through Sony’s (now MAGIX's) automated systems. Historical and Modern Context
Do you still have access to the used for the purchase? Which Windows version are you currently running?
If your account was not migrated, look through your email history for the terms "Sony Creative Software," "Vegas Pro 13," or "Purchase Confirmation." Original digital receipts contain the serial number required to generate your activation. 3. Inspect Physical Packaging