2 NIIIO2- + MnVIO42- + 4 H+ 2 NVO3- + (MnII)2+ + 2 H2O

This is an oxidation-reduction (redox) reaction:

MnVI + 4 e- MnII (reduction)

2 NIII - 4 e- 2 NV (oxidation)

Change the oxidation states