I don't think that version of IOS supports the ip flow ingress and egress commands. You'll have to use the "ip route-cache flow" command. That command only captures data on the inbound traffic, so to see both inbound and outbound traffic, you'll need to put the command on both the ethernet and serial interface of the router. Hope this helps.
I'm not sure I understand your question, but if you mean how will you see traffic coming into both sides of the router, you'll have to add the ip route-cache flow statement to each interface's config. If this isn't what you mean, just let me know.
config t
(config)#int ser0/0
(config-if)#ip route-cache flow
(config-if)#int fa0/0