Cr2IVO4 + 2 KNVO3 + 4 KOH 2 KNIIIO2 + 2 K2CrVIO4 + 2 H2O

This is an oxidation-reduction (redox) reaction:

2 NV + 4 e- 2 NIII (reduction)

2 CrIV - 4 e- 2 CrVI (oxidation)

Change the oxidation states