Hi,
The above example can be converted in ASA 8.3+ as:-
object network obj-192.168.240.240
host 192.168.240.240
nat (inside,outside) static interface service udp ntp ntp
Also , create the ACL on the outside interface and remember to change the destination PI address to the private IP.
Refer:-
http://www.cisco.com/c/en/us/td/docs/security/asa/asa83/upgrading/migrating.html
Thanks and Regards,
Vibhor Amrodia