Thanks Marvin I just ran the script but i got an error message on standby with an error message '' Error restoring health metrics'' hardware is 2500 but i chose 2600 on vm   just to fool the migration tools 

@Marvin Rhoads After fooling the fmc I am still getting error message this error ''Restore will not be available: Product model mismatch'' while  i try to restore.

Thanks Mavin, Is any further steps require after fooling the fmc and  restore the backup on target device ?do we need migration tools ?