How can I upload a file using Express and how would I use integers?

Question

I have created a program using replit.com (it is a Fahrenheit to Centigrade converter), here is the link: https://replit.com/@MJGM2022/f2cCalculator-1?v=1

Everything is working except I cannot figure out how to upload a file via Express, I need a file called f2cCalculator.js

I also cannot figure out how to get the program to output an integer instead of a number with 15 decimal places. I am aware of how to minimize decimal places using .toFixed() but I am not trying to minimize the decimal places, I want the results to display an integer.