To find the missing exponent in the expression \( 10^x = 1,000 \), we need to express 1,000 as a power of 10.
We can rewrite 1,000 as:
\[ 1,000 = 10^3 \]
Now we have:
\[ 10^x = 10^3 \]
Since the bases are the same, we can equate the exponents:
\[ x = 3 \]
Therefore, the missing exponent is 3.