We have,
Smallest number of 4 digits = 1000
Using the long division method, we have

From long division method it is clear that, 1000 is not a perfect square and the obtained square root is between 31 and 32
So, by squaring the next integer we will get the perfect square
(32)2 = 1024
Thus, 1024 is the smallest four digit perfect square
As,
\(\sqrt{1024}=32\)