Slope intercept form follows this general equation...

With this information you have posted, all you can do is find slope, your m. To calculate for slope, you need to use this following equation...

Then, you pick one of your coordinate pairs to be 1 and the other to be 2. I will choose the first coordinate pair as 1, so...

You plug in -1 into your slope formula...

Now, to find your y-intercept, or b, you must plug in one of your coordinate pairs. In that equation, you may plug in the values (3,3), so you'll have...

Just solve for b and you will be done