Set the rules
sudo iptables -A INPUT -i eth0 -p tcp --dport 80 -j ACCEPT
sudo iptables -A PREROUTING -t nat -i eth0 -p tcp --dport 80 -j REDIRECT --to-port 3000
On Ubuntu:
sudo apt-get install iptables-persistent
After that, run next commands every time you want save iptables changes permanently:
sudo netfilter-persistent save
sudo netfilter-persistent reload
If the network interface is different