first i install apache2 using following command
sudo apt install apache2.
sudo systemctl start apache2 to run server.
now i want to see on which port my server is running
You probably have not searched a lot about your question, but here are some solutions:
lsof -i list open ports and the corresponding applications.
For a general check if an app is running you could just use
ps aux | grep apache2 or also
There are more solutions over on Server Fault.