I see that a lot of people are trying to find the file location so I decided to write a quick post telling you where it is:
In a normal Ubuntu installation the Tor browser gets installed on the Desktop so you can find the torrc file in the following location:
Home > Desktop > Browser > TorBrowser > Data > Tor
The default torrc file looks like this:
# This file was generated by Tor; if you edit it, comments will not be preserved
# The old torrc file was renamed to torrc.orig.1 or similar, and Tor will ignore it
Hope this was helpful. Have a good one!