In Ubuntu the Apache configuration is located at /etc/apache2. There should be two folders, sites-available and sites-enabled. Inside sites-enabled are symlinks to config files in sites-available.
You simply have to change the document root in your activated configuration. Thats probably/etc/apache2/sites-enabled/000-default
Have a look for DocumentRoot and change it to /var/www/new, then reload your apache.
And also make changes in apache conf file in /etc/apache2/apache2.conf.