Josh from Befordshire says:

There are six combinations possible. Because there are three different numbers, you multiply $3$ by $2$ and then by $1$, which makes $6$.

Joshua says:

I think the answer is six combinations and how I did it was I wrote down all the correct combinations:

853

Jianmin (Henry Park Primary, Singapore) agrees with six combinations, using $3$ x $2$ x $1$.