Why are some of my Minecraft worlds from Xbox 360 not converting to Bedrock Edition on Xbox...

You can use the Minecraft Realms standard or try the steps below first when transferring worlds.

In Minecraft (Bedrock Version), select the Sync Old Worlds button at the bottom of the worlds list in the Play menu. This finds any worlds on the device from the Minecraft: PS4 Edition and displays them below the button.

Select any of the worlds that are displayed to convert it to the Bedrock edition.

After conversion, the world will show up above the Sync Old Worlds button, along with the rest of your Bedrock worlds.

So I think this page lays out what you need.

The problem is that you can't transfer a world directly from Xbox 360 Minecraft to the latest Bedrock edition of Minecraft. You need to transfer it through the Minecraft: Xbox One edition first.

The
details are laid out here

Basically you'll go from Minecraft: 360 Edition > Minecraft: Xbox One Edition > Minecraft (bedrock)

Let us know if you have problems or questions.

You can't transfer it from the memory stick.

Also, you will need to have the "Minecraft Xbox One Edition" game, not the "Minecraft" (without the "Xbox One Edition" in the name).

To transfer your world to the Minecraft Xbox One Edition, start your Xbox 360 Minecraft, and make sure you have the latest version of it installed by having the Xbox 360 connected online to Xbox Live.

The latest Xbox 360 version has a feature to transfer one world at a time to a transfer slot. Upload your world to that transfer slot, and then move to the Xbox One.

Start Minecraft Xbox One Edition. There you will have the option to import a transferred Xbox 360 game from the transfer slot.

Once the world is imported, you can repeat these steps for other worlds you have on the Xbox 360.

After you transferred all your worlds to the Xbox One Edition, you can start the "Bedrock Engine" Minecraft on the Xbox One, and again transfer your worlds from the Xbox One Edition.

If you don't have the Xbox One Edition, but only the Minecraft for Xbox One, please
contact the official support.

Thank you for contact us! I'm Anderson, an Independent Consultant and a Microsoft user like you.

good night

In Minecraft (Bedrock version), select the Sync Ancient Worlds button at the bottom of the world list in the game menu. ...

Select any of the displayed worlds to convert it to the Bedrock edition.

You can only transfer your world from Minecraft 360 Edition to Minecraft One Edition to (new) Minecraft.

Which Minecraft version do you use? For example, Minecraft 360 Edition in (new) Minecraft is not possible.

Only Minecraft 360 Edition to Minecraft One Edition and Minecraft One Edition to
(new) Minecraft

Minecraft 360 Edition and Minecraft One Edition are out of support and now the Legacy Editions. New Minecraft is the Bedrock Edition