I found directions on the Firefox web site to install. See if this matches your package and where you extracted Firefox to.
First post where you currently have the Firefox package on your system. The package should be called
firefox-1.0.installer.tar.gz.
If you were able to run the command
mkdir -p /usr/local/internet/firefox, then use your file manager to navigate to that directory and see if it is there.
Have you extracted the package yet? If so where? The directory, after extracting it should be called
firefox-installer and should be in the same directory as the gz package.
These are instructions, for reference for us to use later. ignore them for now;
tar -xzvf firefox-1.0.installer.tar.gz
cd firefox-installer
./firefox-installer