With the new update, all the DOM stuff you do should be done with ReactDOM instead of React. It’s a separate module.
Do npm install react-dom and then, if you’re using ES6, you can do:
import ReactDOM from 'react-dom';
or if you’re using ES5 you can just do:
var ReactDOM = require('react-dom');
and then you can use ReactDOM.render(), ReactDOM.findDOMNode(), etc in your code.