Store TinyGPS++ latitude value into a variable of type string or float
it returns me Tiny lat:33.55 on serial monitor. But i want 33.546600. How do I do that? 


The issue is simply the number of decimal places. That can be added to the Serial.println(). 

double Tiny_latitude = (gps.location.lat());
Serial.print("Tiny lat:");
Serial.println(Tiny_latitude, 6);  



  Now if i want to make a String "your location is \nlat:33.546600 \nlong: 75.456912" , i.e. my String variable are stored in Tiny_latitude and Tiny_longitude and want to make a string my_Location. How do i do that?


I would use sprintf() for that but as that requires some additional build parameters the easiest way is to use String. Some special care is needed to increase the number of decimal places. 

void loop() 
{ 
  ...
  float latitude = 33.546600;
  float longitude = 75.456912;
  String buf;
  buf += F("your location is \nlat:");
  buf += String(latitude, 6);
  buf += F("\nlong:");
  buf += String(longitude, 6);
  Serial.println(buf);
  ...
}


Cheers!