To find the area of a rectangle, you can use the formula:
\[ \text{Area} = \text{length} \times \text{width} \]
For Jacinda's rectangle with a length of 6 cm and a width of 3 cm, the calculation is:
\[ \text{Area} = 6 , \text{cm} \times 3 , \text{cm} = 18 , \text{cm}^2 \]
Thus, the area of the rectangle is 18 cm².