HP - ProBook 15.6" Laptop - Intel Core i5 - 8GB Memory - 256GB Solid State Drive - Black. I want to buy this. But does it also have a HDMI Port?

Best way is to Google the model and look for technical specs.

Please Google it.

HP 450 G5 Highlights 1.6 GHz Intel Core i5-8250U Quad-Core 8GB DDR4 RAM | 256GB PCIe M.2 SSD 15.6" 1920 x 1080 SVA Display Integrated Intel UHD Graphics 620 SD/SDHC/SDXC Card Reader USB 3.0 | USB 2.0 | HDMI 1.4b | VGA 802.11ac Wi-Fi | Bluetooth 4.2 Gigabit Ethernet Port Built-In 720p Webcam, Mics, Speakers Windows 10 Pro (64-bit)

I'm not sure why dont you call the store they can help you out very well