How to redirect traffic using iptables?

Question

iptables

Hello dear experts. There are 5 proxies with authorization ( http , socks ) servers
scattered geographically around the planet (all data for example) : 6 server in order to have one incoming ip address and redirect to these 5 servers by ports. Suppose server 6 (main): 6.6.6.6 And so 6.6.6.6:1000 - redirects everything to the proxy 1.1.1.1:9999 6.6.6.6:1001 - redirects everything to the proxy 2.2.2.2:8888 6.6.6.6:1002 - redirects everything to proxy 3.3.3.3:7777 6.6.6.6:1003 - redirects everything to proxy 4.4.4.4:6666 6.6.6.6:1004 - redirects everything to proxy 5.5.5.5:5555

How to organize this using iptables?
I found out that this is iptables PREROUTING POSTROUTING FORWARD
But how to correctly compose the rules themselves, the brute force did not work.

Answer 1

iptables -t nat -A PREROUTING -p tcp --dport 1000 -j DNAT --to-destination 1.1.1.1:9999

Answer 2

POSTROUTING not required?

Required if 6.6.6.6:1000 is not a gateway for 1.1.1.1:9999 (which is not according to the task description).
iptables -t nat -A POSTROUTING -p tcp --dport 1000 -j SNAT --to-
source this answer is trash).