You need to connect an older printer to your computer. The printer connects using a serial connection. Which of the following types of cables do you need?
A DB9 (also called DE9) connector is a type of connection commonly used in serial ports. It is used in many applications including video output, network ports and communication ports such as for printer connections.
Wikipedia
The D-subminiature or D-sub is a common type of electrical connector. They are named for their characteristic D-shaped metal shield. When they were introduced, D-subs were among the smallest connectors used on computer systems.