Can anyone point me to a straightforward guide on how to upgrade from 1.1.10 to 3.x whilst retaining all attachments.
No, not really. You cannot upgrade, you need to export your Vanilla 1 installation and import it in a brand new Vanilla 3 installation. Look at the documentation.
Do it in a test install and report problems (if any) with your attachments. We see if we can solve it anyhow 🙂
I used Porter to import all of the categories and posts from the old version 1.1.10 into 3.0.1.
I also copied the uploads folder from the previous site to the new site.
The attachments are not showing up with the posts in the new site.
I checked the database and the table "Media" exists and is populated with the links to the attachments.
Is there a way to now associate the attachments with their original posts?