Question

In addition to speed, what else we know to predict the position of a moving body ?

Answer 1

In addition to speed. you should know the direction of motion, acceleration, time elapsed after the start of the motion to predict  the position of a moving body.

Answer 2

we need to know the instantaneous speed and the direction of movement of the body.  We can then find the acceleration of the body.

We can then determine the instantaneous displacement or position of the body at any time t.

we need the speed and direction at every point of time.