Cannot find resource

Resource not found: The following package was not found in
I have tried the solutions mentioned in the other posts like putting the PX-4 folder in workspace and catkin_make it still it doesnt work
There is only a folder called sitl_gazebo-classic where models and worlds exist but ,referencing that in the launch file also doesnt seem to fix the problem.
Any solutions ,I use ROS noetic and gazebo 11

Hi! Maybe can you take a step back and quickly explain what you’re trying to do and what command you ran, or which docs you followed? Otherwise it’s hard to know what exactly the error is.

I tried installing px4 in my catkin_ws after these errors and tried catkin_make after it was setup.In the mavros_posix… launch file after i referenced the directory sitl_gazebo-classic which was in px4 rather than mavlink_sitl_gazebo I do not face that error