Can you be more specific as exactly what your existing configuration is and
what you trying to do?
If you are running ODK Aggregate 0.9.x, you should first upgrade to ODK
Aggregate 0.9.8.1.
Then use the ODK Briefcase tool to download data from that instance to your
local desktop.
Then you can deploy a ODK Aggregate 1.2 server and use ODK Briefcase to
upload the data into that server.