The PlayStation 4 Pro has three USB ports.
The ports are arranged with two USB ports on the front of the console and a third USB port on the rear. They use the USB 3.1 standard, providing faster connectivity than the USB 3.0 ports found on the original PlayStation 4. The rear port is particularly useful for accessories that remain connected, such as the PlayStation Camera or an external storage device.
The number is easy to mix up because the PS4 family does not have one universal port layout. The original PS4 has two front USB ports, and the PS4 Slim also has two. The Pro is the model that adds a third port, matching its more performance-focused design and support for enhanced PlayStation VR setups.
The PS4 Pro launched in November 2016 as a higher-powered revision of the PS4. Its upgraded graphics processor supported higher-resolution output and checkerboard rendering in compatible games, but the extra USB port—not the console’s storage capacity—is the key detail in this question.