So I'm not sure how to draw a square with the area of 3 units

The area of a square is width x height where both the width and height is the same length because a square has the same lengths on all four sides.

So we can say “3 = L x L” where L is any side length of the square

L times L is just simplified to L squared: “3 = L^2”

We can take the square root of both sides to get rid of the L squared. We are left with “the square root of 3 equals L”.
Sqrt(3) = L

And on a calculator the square root of 3 is 1.73205080757.

1.73205080757 = L.

The square is 4 lines in a box each with the length of 1.73205080757 units.