If the line is perpendicular to "y= -3x +2" its slope must be the opposite reciprocal of the -3. The opposite reciprocal of -3 is 1/3 so that is the slope of your line.
Now utilize y=mx+b and your point (3,-1) to find the y intercept.
-1=1/3(3)+b
b=-2
Equation: y=1/3x-2
