If the two points shared an x or y coordinate (ex. (2,3) and (-4,3) or (-1,4) and (-1,2)) you can count the units between them.
If the two points do not share an x or y coordinate, then you could use the distance formula, which is this: √(x2-x1)^2 + (y2-y1)^2
If my two points were (0,3) and (1,4) using the distance formula the points are approximately 1.414 units apart:
√(1-0)^2+(4-3)^2 = √1+1 = √2 = 1.414
I hope this helps!