migration to iptables

Hi all,
I used to use ipchains like
ipchains -A forward -j MASQ
to share internet connection. Now on Linux kernel 2.4.18 on Mdk 8.2 I want to try iptables for a while.
I just substitued ipchains in the above command with iptables iptables -A forward -j MASQ
iptables v1.2.5: Couldn't load target `MASQ':/lib/iptables/libipt_MASQ.so:
cannot open shared object file: No such file or directory

I heard MASQ cannot be used like this here. How do I use iptables for the same purpose as for ipchains.
Thanks a lot in advance and sorry for the non-techinicality of the mail :) Thanks and bye.
-Payal