Mass update for destination IPs

I changed my whole Network equipment and created VLANs etc. So did the work now with the change.

The problem is that I have more than 30hosts where I should change the third octet from 2 to 1.
So 192.168.2.xy to 192.168.1.xy.

Is there any way to do that easily? Or should I do it manually for all of them?