So . . . FTP traffic inbound for, say, 9.9.9.9 should go to 10.10.10.10? Create a static NAT entry.
Or do you mean that you want incoming FTP traffic from, say, 9.9.9.1 and 9.9.9.2 and 9.9.9.3 to all go to 10.10.10.10? That's a policy routing issue.
Which is it? I'm too lazy and stupid to try to respond to both.
Steve