On the LG G7 ThinQ with System Update 7:
Settings Icon -> System -> Restart & reset -> Factory data reset
Most other LG phone models should be similar.
Thank you for giving us the opportunity to assist you with this device concern today! We'd love to help you find out how to fully reset your device, and in doing so, we'd like to ask some questions. What happened to the device that you needed to reset it? Which model LG phone are you working with?