2 KNVO3 + Cr2IIIO3 + 2 KOH 2 NIIO + 2 K2CrVIO4 + H2O

This is an oxidation-reduction (redox) reaction:

2 NV + 6 e- 2 NII (reduction)

2 CrIII - 6 e- 2 CrVI (oxidation)

Change the oxidation states