I'm on BC 28 and I setup the External File Account using a blob storage. and I want to move Document attachments to blob storage. how to do that?
Also there's no file scenarios to select.

I'm on BC 28 and I setup the External File Account using a blob storage. and I want to move Document attachments to blob storage. how to do that?
Also there's no file scenarios to select.
I'd refer to this link: Store document attachments in external file storage - Business Central | Microsoft Learn
You want to setup an External file account and after that you need to setup external file scenarios afterwards from the “File Scenario Assignment” page.
If you are having issues accessing pages you may want to review your assigned permissions or consult with a partner who can help configure azure blob storage.
Best,