Minecraft addons bought on xbox 360 gone

DLC for Minecraft works for Xbox 360 and Xbox one edition. it doesn't work for bedrock version.

I´ve bought a new version of Minecraft today, and found out that my microsoft account has no dlcs for the game, despite the fact that I´ve bought many dlcs for the game on the xbox 360 many years ago. So I went to my account and found out Microsoft
doesn´t show anything from xbox 360 anymore, is there a way for me to use the things I bought there on new versions?

Hello, Fello gamer!

My name is Kai and I understand your situation to clarify I do not think there is any way to have dlcs from your xbox 360 onto your Xbox one and Minecraft Xbox 360 isn't compatible with Xbox One so you wouldn't be able to have dlcs from Xbox 360 onto Xbox
One.

You may be able to get a possible refund if you have proof of the purchase by contacting Xbox support:

https://beta.support.xbox.com/contact-us

*in Conclusion because you cannot play a Minecraft Xbox 360 game on Xbox one you won't be able to have the dlcs transferred onto the account to.*

Have a nice day, stay cool ツ

Please contact support from Mojang https://help.mojang.com/

The new version is the "Bedrock" version. You would not find additional content in the Microsoft Store, like you did with the Xbox 360. Additional content would instead be found in the built in Minecraft Marketplace, where you can use "Minecoins" to purchase
a wide variety of user-created world's, skin packs, etc. With this much of a change in additional content, this is why it is not possible to transfer your old purchases over to the new Bedrock version. It may be possible with the old Xbox One edition, however.

This is correct.
This has some more information on the updates when they migrated from discrete versions per platform to the "bedrock" edition. The purchases made with the older version (360) are not forward compatible and there is no way to restore/recover those purchases
in different/newer versions.