How can I find the urdf_tutorial display.launch file

edit

Maybe you should clarify you question a bit...

I interpret your question a bit, hopefully the answer you expected: Now I assume you can run on your system the following launch

roslaunch urdf_tutorial display.launch

Now you would like to know where the display.launch lies in your file system.

Being able to run

roslaunch urdf_tutorial display.launch

means there is a package urdf_tutorial (In this case it comes along with installation; but answer is valid for any package). On your system. You can enter

roscd urdf_tutorial

to navigate to the package folder. Now it is a good practice to put launch files in the launch sub folder of the package folder. If the package follows this you should see a launch folder when typing

ls

in the urdf_tutorial folder. And when entering the launch folder

cd launch

and typing

ls

you should see the display.launch.

Addition:

You can also run

find -L . -name "display.launch"

in the urdf_tutorial folder to look for the display.launch (in case it is not in the launch folder)