Migrating from JD Edwards solution to SAP can be a very complex process. It would be better to understand the business flows you have currently with any unique customizations in the current JD Edwards application and determine how these could be implemented in your target SAP Systems.
Once this is in place, you can determine the necessary data unload/reload to your target SAP system. The mapping of legacy JD Edwards system data to SAP is a long difficult process, and choices must be made as to what data gets moved and what gets left behind. The only way to verify what you need to actually run in SAP environment is to migrate the data over to SAP development and test environments and test it. The only way to get a smooth transition to SAP system, is to develop processes as automatic as possible to migrate the data from the old system to the new. The scope of a data migration project is a fairly large development process with a lot of proprietary code written to extract legacy data, transform and load the data into SAP system.
Stravis has developed adaptors for migrating data from JD Edwards EnterpriseOne and JD Edwards World to SAP.