This will create a file on the desktop with all of the lines that have "location" in them (for example if your Windows user account name is Mitch). Be sure to use the correct path and filenames.
Note that > "C:\users\Mitch\Desktop\Only_Location_Lines.txt"
redirects the output from the screen, and instead puts it in a file. You can leave that off if you want to see the output in the command prompt. That's a good way to test it first. findstr "location" "C:\users\Mitch\Desktop\TheFile.txt"