It is not clear what exactly the question is here. So I guess:
You are missing ARDUINO 1.8.8 2018.12.07? What is wrong with the newer 1.8.19 2021.12.20 Version?
www.arduino.cc/en/software
I assume that the microcontroller from microchip is the ATmega32u4,
which is well documented at Microchip and you can also download a library for USB there.
www.microchip.com/en-us/product/ATmega32U4
www.microchip.com/en-us/application-notes/an7645
ARD MICRO WOH Arduino Micro, ATmega32u4, microUSB, without header
www.adafruit.com/product/1315
alternate shop link
For more technical details and starting guides, check out the Arduino website
docs.arduino.cc/hardware/micro