Will old Xbox One dlc codes work on series X

If the codes were already used, they can't been re-used. Codes are one time use only.

If your game code only says it is for Series X|S then it will not work on an Xbox One X. The One X was the revised Xbox One hardware released in 2017, it's not the same as a Series X.

I am thinking of buying hogwarts legacy as a digital game but it is sold out for Xbox one so should I buy the Series X game and put the code in the Xbox one Store?

No. The series X/S version of the game will only work on the Series X or S.

The only way that would work is if it's a code for the digital deluxe version of the game (which comes with both the series x/s and xbox one versions of the game)

It is worth of trade in old xbox one on the new series x because the series x are better than the xbox one.

Hi,

• You can play disc based Xbox One and BC games on a Series X. The Series S does not have a Blu-ray drive. Series S is a digital only console. You can't play discs on it.
• Xbox accounts work on Xbox 360, Xbox One, Windows 10, Series X and S. All you need to do is sign in. All your digital games/DLCs, achievements and save games come with you. You don't need a separate account for Series X/S. In addition, your Xbox account
  will continue to function on any of your old consoles. You just won't be able to sign in on two devices with one account at the same time.