all of them you have to get 4 of the same candies in a row for a chance but i cant seem to win one tonight normally i can win one fairly quickly just keep trying
People have reported getting the trophy on Level 1, so it can appear anytime after you get your 4-of-a-kind match. I had 3 days when I had 5 shots at the trophy, but I haven't seen it at all in the 2 weeks since. You have to keep at it.
If you're primarily after the trophy, I do recommend quitting and starting over once matching 4 becomes too hard. Sticking with it into higher levels hasn't paid off for me - I won my 3 trophies in the Level 3 to 6 range during my "streak".