The scale factor used to create the dilation is 3
You can easily find out by counting the sides
The coordinates of the pre-image are
(-2,-1) , (-2,1) , (-5,1)
the vertical line counts to 2 boxes
the horizontal line counts to 3 boxes
The coordinates of the image are
(4,-1) , (4,5) , (-5,5)
the vertical line counts to 6 boxes
the horizontal line counts to 9 boxes
= 3
= 3
The scale factor is 3