well done

For anyone looking through the comments maybe even 2 years later like me, Here is some more info. Nothing concise or well written just some notes that may help you. It isn't anything close to an answer but should help hopefully.

00-09 - 00, 01, 02 ... 09
10-15 - 0a, 0b, 0c, 0d, 0e, 0f
16 - 25 - 10, 11, 12, 13, ... 19
26 - 31 - 1a, 1b, 1c, ... 1f
32 - 41 - 20 ... 29
42 ... 255 - 2a ... ff

This is a code-golf challenge which is all about compressing the code to its shortest.

The limit of bytes is 83 and limit of lines is 1.

Also yes 35 lines is a lot

Refer to the example on the description and the sample tests.

The same way you convert any base to another. Alternatively, you'd need to do research and... you know... learn. :)