This is a complex question that I recommend you address fully with Asana Sales or Asana Support.
Did you know Asana orgs can have more than one domain name attached to them? Maybe you don’t need to migrate. That would be key to avoid, if possible, because it will be far simpler to address that way, if feasible.
If you do need to migrate, see the link here:
but recognize that topic/posts are not the same request as yours, though perhaps that one link is relevant.
I don’t think any of the third-party solutions are a 100% migration, but certainly some are better than others.
Thanks,
Larry