Service File can be found at /lib/systemd/system on Pi

DHT11 temp Sensor guide: https://www.freva.com/dht11-temperature-and-humidity-sensor-on-raspberry-pi/

Find an accurate broadcom pinout here https://www.etechnophiles.com/raspberry-pi-3-b-pinout-with-gpio-functions-schematic-and-specs-in-detail/