I have issued a 3-day pay or quit. The tenants have begun moving out. Can I change the locks on the 4th day after issuing the 3 day?

Please don't piggyback your question onto another thread. I've taken the liberty of moving your post to its own thread.

No, you cannot change the locks. That is illegal. If the tenants have not completely moved out or paid by the 4th day then you can file a lawsuit for eviction. If they return the keys to you before the court date then you can have the lawsuit dismissed and then change the locks.

No, you can not change the locks. If they are not out within the three days you can go to court for a eviction from the court.