Cannot find source file in VS Code

Hi Guys,

I am new to this field and have a quite dumb question at the beginning. I follow the instruction page and tried to use VS Code to build the code. But I found that
#include <uORB/topics/sensor_combined.h>
#include <uORB/topics/vehicle_attitude.h>
reported an error that “cannot find the source file”. I tried my best to search these files in the Firmware folder, but end up with nothing.

Can someone help me out? thanks a lot!