How do you find velocity on a position/time graph?

Well, to find velocity, you need to divide the change in position by the change in time. So on your graph, find two points. Find the change in position and time in those two points, these can be any two points on the graph. Then you can divide the change in position by the change in time. (I know this explanation is confusing so hopefully what I included below can help.)

Velocity =   x1 - x2  divided by t1 - t2

x1 = final position   x2 = initial position

t1 = final time          t2 = initial time

Hopefully this helps!