Earth's magnetic field may be supposed to be due to a small bar magnet located at the centre of the earth. If the magnetic field at a point on the magnetic equator is  $0.3\times {10}^{-4}T$. Magnet moment of bar magnet is: (Radius of earth= 64000 Km)

When a magnet is freely suspended in earth’s magnetic field, it's north pole points north, so the magnetic field of the earth may be suppose to be due to a magnetic dipole with it's south pole towards north and as equatorial point is on the broad side on position of the dipole.

$B_e=\frac{{\mu }_0}{4\pi }\cdot \frac{M}{r^3}$

$\begin{array}{l}\Rightarrow 0.3\times {10}^{-4}={10}^{-7}\times \frac{M}{{\left(6.4\times {10}^6\right)}^3}\\ \Rightarrow M=7.8\times {10}^{22}A-m^2\end{array}$