The GCF of $\displaystyle{30}{{m}}^{{4}}\usepackage{cmbright}\Huge\$ and $\displaystyle{36}{{m}}^{{6}}\usepackage{cmbright}\Huge\$ is $\displaystyle{6}{{m}}^{?}\usepackage{cmbright}\Huge\$ .

The missing exponent is _____.