The given function is

A piecewise function is a function that behaves differently on each interval. In this case, we have three intervals with three different behaviors, so let's graph each of them.
First part. 1/3x + 1.
We have to find coordinated points for the values x = -4 and x = -3. To do so, we have to evaluate the expression for each value.

So we have two points for the first expression: (-4, -1/3) and (-3, 0).
Second part. x - 3.
Let's evaluate the expression for x = -1 and x = 0.

The points are (-1, -4) and (0, -3).
For the third part, we don't have to evaluate any expression because the function, in that interval, is a horizontal line.
Now, we just have to graph all the points on the same coordinated plane, as the image below shows.