Hey Boonie!

Not sure what they mean by 'best' prediction but every time you roll a die you get a 1 in 6 (or 1/6) chance that you roll a six. So if you roll it 6 times you just have to multiple 1/6 by 6 So

1/6 * 6 = 1

So my guess would be 1. I hope that helps boonie.