Cu3N2-III + 8 HNVO3 2 N2IO + 3 Cu(NVO3)2 + 4 H2O

This is an oxidation-reduction (redox) reaction:

2 N-III - 8 e- 2 NI (oxidation)

2 NV + 8 e- 2 NI (reduction)

Change the oxidation states