How do you set a goal for a workflow?

How do you set a goal for a workflow?

I am building out a workflow in Zoho Campaigns, and I would like to learn how to set a workflow "goal" so once that goal is met, the user exits the campaign.

Furthermore, I would like the "goal" to be a purchase made through our Stripe account (that we need to link).

Therefore, the lead will continue through the workflow until the user unsubscribes or makes a purchase.

Can you please let me know how to do this?

Thank you