1. I'm too lazy to search for datasheets to compare LM35 to TMP36 sensors
However I would like to confirm if I did it right
So read datasheets and check the maths. Do a calibration test with known temperatures over the whole range.
Add a time keeping function just like commercial dataloggers. Meaning, serial will print the temperature and the time since the start of the experiment.
"commercial dataloggers" would apply RealTime timestamps, which is not available in a standard Arduino.
The "time since start of the experiment" is easier: take millis() and divide by 1000.
Spoonfeeding: Add Serial.print ( millis() / 1000); Serial.print (" s : ");
bfore your line Serial.println(temperature); //printing the result
Getting hours/minutes/seconds from the number of seconds is beyond spoonfeeding.
If you're interested in that, give it a try yourself and only ask for help when really stuck.