be more specific... your question looks like homework.

you can convert any number to any base...
if you know how to convert decimal to hex, bin to hex, etc, you can use the same principle and invent your own base system.

ASCII base 36? maybe counting from 0 to z... 36 simbols, so it's base 36 (0 to 9 base 10, 0 to f base 16... get it?)

research about the "itoa" function (C language)