Resource not found: xacro

edit

I am a beginner at using ROS.

I just following the "Building a Visual Robot Model with URDF from Scratch"

Already:

created tutorial_ws/src

downloaded and copied the urdf_tutorial to src folder

cd tutorial_ws

catkin_make

source devel/setup.bash

roslaunch urdf_tutorial display.launch model:='$(find urdf_tutorial)/urdf/01-myfirst.urdf'

However, I have an error: Resource not found: xacro

Do I miss any steps? Thank you in advance for your help!