Answer
$1000$
Work Step by Step
The generalized basic counting principle says that an event $e_1$ can be performed in $n_1$ ways and an event $e_2$ can be performed in $n_2$ ways, then there are $n_1n_2$ ways of performing them together. This can easily be extended to $n$ events.
Here we have $10$ choices for all $3$ digits, thus using the generalized basic counting principle the number ways: $10^3=1000$
