If you have a new computer or laptop, there is a chance that you may not have a serial port in your computer. The new computers or laptops sold today do not include serial or printer ports. The serial ports have been replaced by Universal Serial Bus (USB) ports.
If you want to connect to the console port of your router or switch, you will need to use a USB to Serial Adapter. The USB to Serial adapter may not be plug-and-play. You need to install the corresponding drivers also for these adapters. A typical USB to Serial adapter with console cable is shown below.