I have a “Personal Projects” free workspace I created a long time ago (2014). I am the only member. The email uses a custom tld, not a gmail, etc.
I want to convert it to an org, but when I am in that workspace, there is no “Admin console” link (or “Upgrade” button) when clicking on my profile icon.
These do exist, as expected, in other orgs that I am an owner of.
I actually tried just inserting my workspace id into the admin url Log in - Asana but it gave me a " It looks like you don’t have access to this" page.
I think your best bet would be to contact support@asana.com with your question.
The “Personal Projects” workspace was actually deprecated quite a while ago, so I think Support will be the best ones to advise you of your options.
Should you need to actually transfer/migrate projects, as part of your solution, the recommended app is ditto.kothar.net for that; be sure to read the help/caveats there; it’s a great tool but good to read about limitations that could affect you.