The most basic oxide among MnO, MnO2, Mn2O3, Mn2O7 is_______.

Please explain.

Can we find it by using oxidation state?

Yes, the answer to the above question can be given on the basis of the oxidation state.
Generally, for transition metal oxides, the lowest oxidation state is the most basic, since it can donate lone pairs of electrons and function as a Lewis base. Higher oxidation states are short of electrons, meaning they can accept lone pairs and function as Lewis acids.

MnO has the lowest oxidation state, so it is the most basic. Mn2O3 is next, then MnO2, and finally Mn2O7 (which is actually acidic).