can you include functional components in existing pages react code example

Example 1: functional component react

function Welcome(props) {
  return 
Hello, {props.name}
;
}

function App() {
  return (
    

                      
  );
}

ReactDOM.render(
  ,
  document.getElementById('root')
);

Example 2: create-react-app class component

npx create-react-app my-app --scripts-version [email protected]