Approx. 8 feet long. According to the internet:
Multi-pin connector cable, commonly used in computer systems and electronic devices to connect various components. The specific type of connector is known as a Molex connector, which is often used to connect power to internal computer components such as hard drives, optical drives, and sometimes even fans.
Has one female connector with four pins and another smaller 3-pin female connector, possibly for a fan or another small device that requires power. The 4-pin Molex connector is standard for providing power to drives, and the smaller 3-pin connector is typically for providing power to smaller devices or for connecting fans that do not require as much power.
It's usually meant to plug into the power supply unit (PSU) and then into the appropriate device that requires power. Always ensure the computer is turned off and unplugged before attempting to connect or disconnect these types of cables.