Probability of each combination with repetition

Hi guys,

It looks like trivial problem but I cannot solve it.

I have M baskets and N balls. I can choose one of the baskets randomly and put a ball into the chosen basket.

I'm just interested in combination. So in three baskets with 5 balls,

(1) (1) (3)

(1) (3) (1)

(3) (1) (1)

above combinations are same for me.

I just want to know the probability of each combinations. I know that all possible combination can be represented by combination with repetition.

But I do not know that how many cases of each combinations are existed.

Any helps are appreciated!!!

Thanks in advance!