Thank you for quick reply.
ok for me it was actually /Android/data/bruenor.magicbox/files/.MagicBox/Games/Data/[cryptic profile name]/Screenshots.
and I noticed that if I set title image for each game, it will store copy of it as avatar.png in [cryptic profile name]folder so it would be easier way to locate the profile I want.(this is for others if they encounter same need as I did)