Installation guide from Data Migrator
Data Migrator is an ISV application that should be installed in your Production organization (or the organization which has the data to be exported). Data Migrator uses the current installed organization as the source organization to extract the data and pushes the data to the target organization.
The application can be found here:
Data Migrator does not store the credentials of the target organization. Data Migrator will always prompt for credentials during every migration.