Open file explorer outside of VS and search for the names. For example, on my Windows 10 laptop I found:
“Arduino.h” located at C:\Program Files (x86)\Arduino\hardware\arduino\avr\cores\arduino
“WiFi.h” at C:\Users\prock\.platformio\packages\framework-esp8266-nonos-sdk\examples\esp_mqtt_proj\include\modules
… etc.
I also modified paths in “System Environment Variables” so that these files are automatically found at startup in VS.

Thanks Tom … I found it where you stated.  (I had tried the search for Arduino.h, but my Windows 10 comes up with “see web results” … don’t know why.  Also I don’t have those locations in my PATH, but VS comes up fine – why do did you do that?)
This topic can be closed

Welcome Joe! Sorry you are still having issues. 
PATH — I started to have VS compilations errors where could not find certain *.h files. So I located all of the files then manually modified my PATH in “Env Vars” to include paths to all required *.h files. Errors when away.
Have you searched every drive including ones on clouds like OneDrive? My PATH problem started when somehow my Arduino files were installed on my OneDrive.

Thanks Tom.  Actually, I finally realized that what I needed was a good reference manual to the ESP32.  I had questions about the ledc (led controller), and thought the .h files would help specify that; now that I can see some of those .h files, it really doesn’t help much. For example, the ledc (led controller) functionality is really an Espressif-provided function, best explained in the reference manual (section 13 in this case).  For anyone reading this and wanting access to the manual, here is a link to the pdf: http://usermanual.wiki/Document/esp32technicalreferencemanualen.364707200.pdf   (an example – PWM is described in the eBooks using ledc for leds and motors, but there is also the MCPWM module to control motors; worth a look)

Actually the best location for the ESP32 would be at Espressif’s web site – https://docs.espressif.com/projects/esp-idf/en/latest/esp32s2/index.html

yes indeed!  Thanks Steve. .. the hardware manual I was looking for was buried down in the page: https://docs.espressif.com/projects/esp-idf/en/latest/esp32s2/hw-reference/index.html … good documentation by Espressif 🙂  (unlike the documentation for the “guts” of the Raspberry Pi)

Hi.
I see you already solved your issue.
I’ll mark this issue as resolved.
If you need further help, you just need to open a new question in our forum.
Regards,
Sara