CrIIO + 2 KNVO3 + 2 KOH 2 KNIIIO2 + K2CrVIO4 + H2O

This is an oxidation-reduction (redox) reaction:

2 NV + 4 e- 2 NIII (reduction)

CrII - 4 e- CrVI (oxidation)

Change the oxidation states