To find the scale factor, you can compare the new side length to the original side length.
The original side length of the square is 3 cm, and the enlarged side length is 12 cm.
The scale factor is calculated as follows:
\[ \text{Scale Factor} = \frac{\text{New Side Length}}{\text{Original Side Length}} = \frac{12 , \text{cm}}{3 , \text{cm}} = 4 \]
So, the scale factor used for this enlargement is 4.