Smf 2.1 beta 2 migrate to my mybb

My English is bad, I apologize.
I am using Smf 2.1 beta2
Smf 2.1 has remained in beta for more than two years and the stable version is still not released.
It does not appear to be published.
No system will stay in beta for 2 years.
I think the project will end.
I want to migrate Smf 2.1 to mybb.
But the merge system does not support smf 2.1.
Any ideas on this?
Thanks