Hello, good day and thanks for your question. Sorry to know about this and I understand that you are unable to find the redemption code for the game that you have purchased.
May I check and confirm if you have purchased it from the Microsoft Store or this is from a different platform?
As an initial step, you can check the email account that you have and see if there is an email that is related to your purchase and then check the account that you are using to ensure that you are also on the correct account that was used when you made the purchase.