I am trying to make a game with a save code that's represented like this clicks:clickspresecond:muti:upgrades then encode it to base64, i have a example save code: 67:1:24:2 base64 encoded: Njc6MToyNDoy, but i cant find any projects to hep and i don't know how base64 works

The base64 conversion takes binary data and makes groups of 6 bits which then get converted to the corresponding base64 digit. Going back to the original data is just the same process in reverse.

Here's a table you can refer to for binary to base64 on Wikipedia:
https://en.wikipedia.org/wiki/Base64#Base64_table

Here's a table for ASCII to convert text into binary, also on Wikipedia:
https://en.wikipedia.org/wiki/ASCII#Printable_characters