You can use it, but you should modify or remove variables like ${prefix}. you can do it that what is different compared to ur3. urdf based on ur5.urdf (I used).
If you change the joint or link name, you should change the name in the code then you will see ur3 with robotiq140 in pybullet.
https://github.com/ros-industrial/universal_robot/blob/kinetic-devel/ur_description/urdf/ur3.urdf.xacro
You can use it, but you should modify or remove variables like ${prefix}. you can do it that what is different compared to ur3. urdf based on ur5.urdf (I used).
If you change the joint or link name, you should change the name in the code then you will see ur3 with robotiq140 in pybullet.
Cheers