Could someone explain to me how to get the equation for slope off of a graph? It would be greatly appreciated:)

Ok so how I get slope if doesn’t mention it
I get two pairs from the graph example (2 and 2) and (4 and 4)
When I get two pairs you do x2- x1/ y2-y1
It looks like this 2-2/4-4
2-2= 0 4-4=0
So the slope is is 0 in this one
I hope that helped and you put the equation like this
Y= Mx+b the m is the slope
I hope that helped