Help with iMac ports

it needs hdmi and usb according to the site

https://www.amazon.com/HUION-KAMVAS-Pro-Sensitivity-Bar-15-6inch/dp/B07S7BCTWW

 Connection Tips:

• Your computer needs to have HDMI and USB ports available for the connection, if not, you need an adapter to convert for the connection. Please be assured the USB cable & HDMI cable securely plug into your computer.
• It is only coming with a US power adapter (suit for 110V-240V). If you need EU or other power adapters, please ask us for further information.
• After connecting all the cables to correct places, please wait about 30s-1min to wait the USB Hardware driver loaded successfully.

the hdmi would be the looks of it be hdmi output from the mac

you can get a wide range of thunderbolt 3 to hdmi adaptors https://www.amazon.com/thunderbolt-3-hdmi/s?k=thunderbolt+3+to+hdmi

it's likely not suggesting html as that is the file format of websites such as this

if it's hdmi then it along with dp (display port) are video output ports that you connect monitors to

both usb and thunderbolt would seem reasonable ports to connect input devices such as a digitizer for drawing

if you link to the product in question one could have an easier time deciphering what the tablet really needs