Problem in sending the value of the Get method


I have created a web server with some buttons and I use the get method to each button

and when I push each button I have some message in serial monitor

the message is:
GET /?Turn+On=OTurn+On HTTP/1.1

Now I want to use indexOf function to if I push the button OTurnOn send me the string OKKK
But It does not work

The code I have been written is:

and to be more clear for example one of my definition of button is :

s+="<input class=“button” type=“submit” name=“Turn Off” value=“OTurn Off”>";