User blog comment:High Prince Imrahil/A Brief Question/@comment-27219153-20170126004059

You can't really use Joetater if you're changing mod versions. What you can do though, is put both worlds on the same version and then use Joetater. If you take region files directly from one version of a mod to another, you will likely end up with different block ids, making your fortress be made out of entirely different blocks (Beta 30 - Beta 30.5 should have the same block ids, but not Beta 29 and Beta 30).