Answer:
5 units.
Between A and C there are 5 squares until it reaches C meaning that the distance between points A and C is five units.
If these unit squares on the grid equalled a different number each (for example, 2) then the distance from the said points would be 10 and you can find this by multiplying 5 x 2. If it was any other number then you would do the same (5x).
We can also find the answer to this when only given the points.
Since A = -2, -3 and C = 3, -3 we can already see in this way that their value for y is the same. Since A's value for x is -2 then we can add until we get to 0 and continue adding until we reach 3 (aka C's value for x), this would equal 5 units.
(My condolences for the other answer as I read it incorrectly)