Where might the extension be stored within FreePBX / Asterisk? I’ve looked in the etc/asterisk/extensions.conf file but don’t see them there. For example one of my extension numbers is 200 and when I did a search in Vim for 200 in the etc/asterisk/extension.conf file nothing came up. Please advise
When you looked in /etc/asterisk/extensions.conf did you see the huge notice at the top of the file with this link http://freepbx.org/configuration_files?
You should also check out the wiki.
Much of the confg for FreePBX is stored in databases that are used to generate the config files. There are many files that are included into extensions.conf as well as other standard Asterisk config files.
please check this file sip_additional.conf in /etc/asterisk directory