Sorry for not noticing that you have three IPs from your ISP.
But if you have three routers, each needs to be set to a separate subnet, with its own DHCP server.
So router 1 can be 192.168.1.X, router 2 192.168.2.X and router 3 192.168.3.x.
In this configuration, however, the clients behind each router won't be able to communicate with clients behind another.
If you want to keep some clients protected from an insecure LAN, then use cascaded routers, like described in the article I linked in my previous answer. Or invest in a smart switch that can do VLANs and get rid of the multiple routers.