Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
You can pre-load your Microsoft 365 subscription for up to 5 years.
Log into your Microsoft account on this link:
https://account.microsoft.com/services/
Check the expiry date listed on your Microsoft 365 subscription, is that now indicated as 2029?
If so, you have correctly pre-loaded your subscription for 3 years.
If the expiry date is listed correctly, you can disable the recurring billing on the subscription to ensure no payments are taken from your account during that 3 year time period.