Task name hints us to do something with base. Looking at characters, it may be in a numeral system with base 22 or higher. Let's try 22!
It converts to number `208680969563662669880355405571581710048531200248533882328034699304208685490174848941949` in decimal numeral system. Than we can transform if to bytes, decode and get
>kks{do_y0u_know_h0w_3nc0d1ng_w0rk$?}

Original writeup (https://github.com/4p3ls1n/write-ups/tree/master/kksctf_open_2019/Message%20from%20base).