I don't see you being able to accomplish this as this was never the intent of the OpenStack community. If you want at all to take what you have from Folsom and get it to Juno, you would need to take the iterative steps of going through the upgrade process of each release and even then there maybe be caveats and pitfalls for each release.

Your first step should be to read the release notes of every release and see what they have listed for upgrades.

Folsom->Grizzly->Havana->Icehouse->Juno