3 NaNVO3 + 8 NaOH + 2 Cr2IIIO3 3 NaNIO + 4 Na2CrVIO4 + 4 H2O

This is an oxidation-reduction (redox) reaction:

3 NV + 12 e- 3 NI (reduction)

4 CrIII - 12 e- 4 CrVI (oxidation)

Change the oxidation states