Micro/mini/type-c Usb Atmega32u4 Module 5v 16mhz Board For Arduino Atmega32u4-au/mu Controller Pro-micro Replace Pro Mini - Integrated Circuits - AliExpress
transistors - Questions about the circuit of the Arduino Micro - Electrical Engineering Stack Exchange
Arduino Micro pinout diagram @ pinoutguide.com
Fixing an Arduino Pro Micro: the USB Port Came Off !! : 17 Steps - Instructables