create a backup copy of rman backup file

I have rman backup stored on asm fra area using OEM backup job.

I need to store the backup file to another file system as another copy of it.

My ASM file has following format where oradev is database name.

annnf0_backup_oradev_orad_0427150300_0.22667.878096185

I tried using this, but file name does not match. It does create backup copy of backupset.

backup backupset all format '/mnt/Database/ORADEV/Backup/%U';

What should be format used in this command instead of %U to match backup set name? Where could I see the format used by OEM to generate the backup in ASM FRA?