Port 3000 is closed and not listening

I installed plesk on ubuntu, my project works with port 3000 and other ports which needs to be enabled and also listens, but i am finding it difficult to find out how to really open it and get it to listen. Here is what i have tried:

1. Using sudo ufw allow 3000 directly from ssh

2. Enabling firewall and allowing on ports on plesk

3. Using iptables to add ports. ( When i type in iptables list, it shows that the ports i added are there but when i type in the listening ports, my added ports isn’t included)

My ports are currently added but how do i get them to listen or is there something i’m not doing right?