Hi Fayaz
if you know the procedure to do the migration you can just copy Old USR layer from AX40(axusr.aod) file application to AX50_APP ,to refresh your memory follow this steps from MS AX doc :
AX40 >AX50
1. Install Microsoft Dynamics AX (includes application files, client, AOS, and new empty database).
2. Run the Microsoft Dynamics AX DB Upgrade Preparation Tool from the installation media.
3. Start the AOS.
4. Start the Microsoft Dynamics AX client.
5. Load your license keys by clicking Administration > Setup > System > License information. Then click the Load License File button.
6. Close the Microsoft Dynamics AX client.
7. Click Start > Administrative Tools > Services and stop the AOS (identified in the Service list as the Dynamics AX Object Server).
8. Copy the application files (*.aod) from all layers above the HFX layer to: \Microsoft Dynamics\5.0\Application\Appl\Standard
9. Copy application files (*.aod) from all layers above the HFX layer to: \Microsoft Dynamics\5.0\Application\Appl\Standard\Old
10. Delete the index file (axapd.aoi) from the Standard folder.
11. Start the AOS through the Services list.
12. Start the Microsoft Dynamics AX client.
13. Run through the Upgrade checklist