The httpd.conf file location depend on the operating system which you are using. If you are using the CentOs then location of the file is /etc/httpd/conf/httpd.conf.
Please note, it's not recommended to update the httpd.conf file. If you are very sure about the working of it then only update it. Before making any changes, take the backup of the file. Because if you will remove the single line from the httpd.conf file then overall working of the server will stop.