Instructions
Open a save game converter website such as the Shunyweb Savegames Converter or UniqueGeeks.net NDS and GBA Save File Converters.
Click the "Choose File" button and pick your DUC file.
Select the "Source Format" from the drop-down menu. The exact source may vary depending on what version of the Action Replay generated the DUC file. If you do not have this information, select "Action Replay MAX" and try the other options if it does not work.
Choose "Raw Save" on the "Target Format" menu. For the Shunyweb Savegames Converter, choose "RAW Format [Autodetection]." Alternatively, if you are using a savegame editor or specialized save loading device, you may need to select the appropriate format for your hardware. If you cannot find the right format in the menu, consult your hardware's documentation.
Click the "Convert" button to generate your SAV file.