First find the slope:
Change in y = 2 - (-4) = 6
Change in x = -1 - (-3) = 2
Remember to subtract in the correct order... if you use y1 - y2, then you have to do x1 - x2.
Another note, the order in which you subtract (y1 - y2 or y2 - y1) does not matter.
The slope: 6/2 = 3
To find a parallel slope, you need to remember that it's negative, then reciprocal. In this case:
3 => -3 => -1/3