Let $r$ be the distance from the center of the Earth to the point at height $h$. The gravitational potential $V$ at distance $r$ is given by magnitude $|V| = \frac{GM}{r}$. The acceleration due to gravity $g_h$ at distance $r$ is given by $g_h = \frac{GM}{r^2}$. Dividing the magnitude of potential by the acceleration gives the distance $r$: $\frac{|V|}{g_h} = \frac{GM/r}{GM/r^2} = r$. Substituting the given values: $r = \frac{5.4 \times 10^7 \text{ J/kg}}{6.0 \text{ m/s}^2} = 0.9 \times 10^7 \text{ m} = 9 \times 10^6 \text{ m} = 9000 \text{ km}$. The height $h$ from the surface is $h = r - R$, where $R$ is the Earth's radius (6400 km). $h = 9000 \text{ km} - 6400 \text{ km} = 2600 \text{ km}$.