Can't change the port number.

[Sutharshan-art]

I'm trying to deploy the project and run on Apache server using ubuntu virtual instance. It's running on the default port number 3000. So I need to manually add the port number next to the domain url. I tried to modify the package.json file and changed the port number to 80 and executed. but it's running on the same default port number. Can I get solved this issue?