Ni(CO)4 has no unpaired electrons, hence magnetic moment is null.
[Mn(CN)6]4− has 1 unpaired electron, hence the magnetic moment is 1.73 BM.
[Ni(NH3)6]2+ has 2 unpaired electrons, hence the magnetic moment is 2.82 BM.
[Mn(Cl)4]2− has 5 unpaired electrons, hence the magnetic moment is 5.93 BM.