Need help deriving a convertion function on python

[johnnyukpo at gmail.com]

Good day,

I have a computer programming assignment. I am completely lost and i need some help.

These are the questions that are confusing me 
(a) Write a function which converts from gallons to cups2
(b) Now we’d like to be able to convert from cups to milliliters, since metric measurements
are easier to convert between. Implement a function which does this.
(c) We’d also like to be able to easily convert gallons into milliliters, so implement a
function which does this