Device which will turn off my water motor automatically after the tanks are full
There is no need for fancy electronics here.  Look for something called a float switch.  Various types are readily available in hardware stores.

I have one of these turning on a sump pump in a bucket that my basement sink drains into.  In this case I have a float (a small re-purposed pickle jar if I remember right) connected to a threaded vertical shaft.  That shaft has two pair of opposing nuts on it, which are the stops to activate the float switch to click between on and off.  I can adjust the water level for on and off by adjusting where the nuts are on the threaded shaft.

In my case, the shaft going higher turns on the switch since I'm trying to empty the tank, not fill it.  However, I could have mounted the switch upside down to get the effect you want.  Most switches are either mechanically symmetric so that you can mount them either way, or are available in normally open and normally closed options.