How can I add a confirmation page (Thank You Page) for a specific item/product purchase?

Site URL: https://www.appletreeconnection.com/

I have 2 (course) but 4 available product (based on schedule) for sale and I want to get them directly thru a Thank You page about an instructions on what they should do. So basically there are 2 thank you pages for each specific course the other course has just 3 schedules thats why its a products. I know it need some code injection and just specify some order ID. Now, I don't know how to specify the order ID

<meta http-equiv="refresh" content="10;URL='/thank-you'" />

PLEASE HELP