If you want to convert nanosaur .xacro file to URDF

Install

sudo apt install ros2-foxy-xacro

Convert

~/nanosaur_core/src/nanosaur_simulations/nanosaur_ignition/urdf
xacro nanosaur.ignition.xacro > nanosaur.ignition.urdf

Option convertion

If you want to add an extra option

xacro nanosaur.ignition.xacro covert_type:=realsense > nanosaur.ignition.urdf

Reference:

• https://automaticaddison.com/how-to-convert-a-xacro-file-to-urdf-and-then-to-sdf/