Migrating from Identity Manager to Virtual Appliance has to take into consideration the present configuration.
This technical document deals with the scenario where the user store resides on a database.
Is Migration to Virtual Appliance from Identity Manager possible when the user store resides on a database ?
Virtual Appliance 14.0
On VApp machines, the User Store has to be CA Directory. It is set so from installation.
You will need to migrate from the database you are using to CA Directory.
Then use the directory schema enforced identityEnv environment.