The equation given can be re-written in slope-intercept form as y = (-1/2)x + (5/2)
The slope of the given line is -1/2 and the slope of any line parallel to this one will have equal slope.
The equation you need then is -1/2 = (y - 6)/(x + 3)
Remember slope is the change is y value (sometimes called rise) divided by the change in x value (sometimes called run).
Cross multiplication and collection of terms will give you the standard form: x + 2y -9 = 0
and rearrangement will give you slope-intercept from: y = (-1/2)x + (9/2).