I must assume that your "3x to the second" means (3x)^2, which is equivalent to 9x^2.
Then h(x)=9x^2.
You might make a table of x and y values:
x y
0 0
1 9
2 36
Choose a few negative x values also.
The resulting graph will be that of a parabola with vertex at (0,0), opening upward, symmetrical about the y-axis.