I use this urdf file:

cobotta_pro_900.urdf

located at :

/home/theobloesch/.local/share/ov/pkg/isaac-sim-4.2.0/extscache/omni.importer.urdf-1.14.1+106.0.0.lx64.r.cp310/data/urdf/robots/cobotta_pro_900

that I copied in another folder easier to reach.

Then I followed the step provided in this tutorial: https://docs.omniverse.nvidia.com/isaacsim/latest/advanced_tutorials/tutorial_advanced_adding_new_manipulator.html

1. copy the urdf assets (cobotta_pro_900.urdf, cobotta_pro_900_visualization and onrobot_rg6_visualization) under a new folder URDF_Folder_Path/cobotta_pro_900. These assets could be found at /extscache/omni.importer.urdf-*/data/urdf/robots/cobotta_pro_900
2. Launch Omniverse Isaac Sim using the launcher.
3. Open the URDF Importer through Isaac Utils > Workflows > URDF Importer
4. In the extension window, choose the URDF file under Import > Input File, check Create Physics Scene and Fix Base Link, choose the Joint Drive Type to be Position, and uncheck the Parse Mimic Joint tag.
5. Click on Import in the extension window.

Which gave me this usd file:

cobotta_pro_900.usd