ANSWER
1/3
Step-by-step explanation
The pre-image has coordinates (-3, -6) and the image has coordinates (-1, -2)
The scale factor is the number by which the pre-image was increased or decreased in size through dilation.
To find that, we pick either of the x or y coordinates of the pre-image and image and then we have:

Let us pick the x coordinates.
We have that the scale factor is:

The scale factor is 1/3.