Hi @supriya3198,
Connecting the + terminal of the DHT11 to +3.3V is correct. Here is a good description of what each pin is good for:
D8 is pulled down to GND. That could be the problem. Also, if you are using D8 and you place 8 in your code, that will refer to a nonexistent pin as there is no GPIO8 on the ESP8266.