MAVLINK shell over USB - pymavlink pyserial issues

I am currently using the port "SERIAL 3/4 " connected to a TI TMC123GXL LaunchPad In order to use serial over USB. And then I can connect under linux with : screen /dev/ttyACM0 57600 8N1. And it works fine.

Then I tryed to connect MAVLINK shell on pixhawk by only a simple usb link from the side of the pixhawk hardware to the PC but It does not work :

I am having trouble with installing : pip install pymavlink pyserial

I also saw that there is a port call USB neer the LED , what is this port for ?
Thank you in advance

never mind I figured it out the probelm…

Hey I’m trying to communicate via USB cable from raspberry PI into the USB port on the side of the Pixhawk. I need to do a mavlink stream -s SYSTEM_TIME -d /dev/tty<?????> to stream time through the side usb port on the Pixhawk. Do you know the name of the serial device port that is the USB port on the side of the Pixhawk?