About finding my activation code for Xbox Game Pass Ultimate

If an Xbox Game Pass Ultimate is active, when you redeem a code for Xbox Live Gold or Game Pass for Console it will automatically be converted. In the future, it would be best to make sure that the Xbox Game Pass Ultimate is not active so it will not be converted.

If you had Xbox Game Pass Ultimate already active before you redeem that code, when you enter a code for Xbox Live Gold or Xbox Game Pass it will add as Game Pass Ultimate and not only Xbox Game Pass, is this your case?

It is probably because you previously activated your game pass ultimate subscription. If you redeem a prepaid gold or game pass code while you have active the game pass ultimate subscription, the code will extend the time of the game pass ultimate subscription
but considering a conversion. A 12-month code of Xbox Live Gold extends a 4-month equivalent of a Game Pass Ultimate subscription.

Here is a link that contains information on equivalences.

https://www.xbox.com/live/gold/upgrade

Maybe you bought a code for 3 month of Xbox Game Pass non Game Pass Ultimate.

If is this the case, because you have an active Ultimate subscription and you are triyng to redeem an Xbox Game Pass subscription, there is a conversione due to the different cost between this two plans.

You can find additional info here: https://www.xbox.com/en-US/xbox-game-pass?xr=shellnav#faq

In particular, search for "After I join Xbox Game Pass Ultimate, can I still redeem Xbox Live Gold and Xbox Game Pass codes?" FAQ

You are not forced to use ultimate. If you wanted to go back to Xbox Live Gold you needed first to cancel the ultimate subscription, and then insert the code. For all users, with xbox game pass ultimate active, when you submit a xbox live/xbox game pass
for console/ xbox game pass for pc codes it will automatically convert in xbox game pass ultimate months using the established ratio.