Yes Kelvin. You can use Migration Cockpit for the purpose of migration, but you need to secure the Migration Services from SAP which is a chargeable service. Migration service comprises of Questionnaire before start of migration, Migration cockpit, scenario validation, test validation and weekend development support during migration. You will get more details about this Service in SAP Note 812919.
You will be able to execute the transaction CNV_MBT_NGLM only after migration cockpit is installed in your system. Migration cockpit is the recommended tool for migration of data in New GL.
Regards,
Sridhar
