Arduinos

sudo apt-get update && sudo apt-get upgrade
sudo apt-get install arduino
Tools > Board
Tools > Serial port
Tools > Serial monitor

Mega pinout: https://www.electroschematics.com/wp-content/uploads/2013/01/Arduino-Meg...

Program an Arduino IDE https://magpi.raspberrypi.org/articles/program-arduino-uno-raspberry-pi
HC-SR04 Ultrasonic Distance Sensor and CAD : https://www.makerguides.com/hc-sr04-arduino-tutorial/