Migrate old Kirby 3.3.x with Builder/Editor plugins to 3.7.x - 3.9.x (latest) with native Blocks?

Edit: I see, I found this thread and realized older versions of the documentation have some more information. I’ll submit a PR as I think there should be a link here.

I need to update an old project which is running 3.3.x with Builder/Editor to 3.9.x and am having a bit of trouble figuring out the correct path for this.

I’ve read through the release notes for 3.5-3.7 and looking at the official documentation, it says:

Builder and editor field migration has been removed since Kirby 3.7. If you are upgrading to Kirby 3.7+ from an older version with the builder or editor field, please first upgrade to Kirby 3.6 and migrate your content to the new blocks format.

I’ve updated to but don’t see any kind of migration anywhere.

Then I’ve looked at these threads as well:

One mentions a migration guide and the other mentions automatic migration, but I’m just not able to find it anywhere (looked through release notes in the docs and on github as beast I can) and am just unsure if it’s meant to be a fully manual process of editing the blueprints and trying to run this custom php script or if there is a more official path to the upgrade?

This is the documentation from the 3.6 version of the docs: Blocks | Kirby CMS So theoretically, it should be automatic.

I have also issues with that. If i leave the builder and want to add smth. the add selection is empty but everything works fine. If i change to blocks and add something it gets me this error:
Invalid structure data for "module" field on parent "home"