The coordination geometry around the manganese in...

Around the manganese atom, there are five $CO$ ligands and one Mn occupying octahedron vertices. For octahedral geometry, the more appropriate hybridization is ${d}^{2}{sp}^{3}$ that produces six hybrid orbitals pointing towards $CO$ and $Mn$.

The octahedral shape of molecules is the shape of molecules where six atoms or ligands or groups of atoms are arranged in a systematic way around a central dogma or atom. The Octahedral Shape of Molecules molecules has eight faces.