Question

The gravitational potential difference between the surface of a planet and a point P, 10 m above the
surface, is 8.0 J kg-1. Assuming a uniform field, what is the value of the gravitational field strength
in the region between the planet’s surface and P?

Answer 1

I assume you mean the gradient is uniform. And I assume you have calculus.
You have used terms Potential, and field strength, I hope you used them precisely . Field strength is the gradient of Potential.

Gravitational Field strength=d(potential diff/d height)
or "g"=8(J/kg)/10m=.8J/kg-m

Answer 2

effected region of a mass to attract another mass is called gravitational field