I have installed java and apache tomcat on my Google cloud instance and have started the tomcat but when I try to connect to my instance from my browser on port 8080 or 8443 I cannot connect it. I should see the apache tomcat's welcome page right? Can someone plz help me with this?
You need to configure firewall to allow those ports. The best option for your use case would be to use Google Cloud Launcher. https://console.cloud.google.com/launcher/details/click-to-deploy-images/tomcat.
It should give you an external IP with HTTP and HTTPS tomcat ports open 8080.