You will have been emailed your Steam keys when the game was released on Steam (and a followup reminder for anyone who didn’t activate their keys). If these emailed ended up in your SPAM filter then they’re likely gone. If your account email address matches your purchase email address I will automatically resend your keys. If not, we’ll need to work out your identity and which purchase is yours.
UPDATE: I’ve looked up your purchase and it was for a Trailblazer. Please see this FAQ entry for details for the status of Trailblazer purchases. If you think you also purchased a Pioneer I’d be happy to find it but will need to know which email address the purchase is connected to.