Can you tell me how to identify the SFeVT ID which is needed to complete the Credit Card Charge/Validate URLs for GW Auctions?

This is the complete URL as it appears in the GW Installation Guide:
https://evt.salesforce.cloud.clickandpledge.com?SFOrgID={5 }&SFeVT ID=<you-must-fill-in>&CnPAID=<you-must-fill-in>&SFContactID={0}&b1=Auction%20Purchases&up1={2}&sh owTotal=1&SessionId={3}&ServerURL={4}

Thanks,

Caroline