You will have to ask Costco. Are you sure they did not provide it when you purchased the software?
@jcohen8317 You just tried to post your personal information on a public web site that can be seen by anyone on the internet. Please do not post your name or email here unless you want to hear from scammers and identity thieves who would like to pretend to contact you from TurboTax. The filter removed your SSN and email. Your name is still here.
This is a public web site that can be seen by anyone—including scammers and would-be identity thieves who would love to contact you and pretend to be from TurboTax. Please remove the personal information you posted here ASAP by returning to your post and clicking the three little blue dots on the upper right to edit your post.