What type of cable do I need to go from my iPad Pro to my TV's HDMI input?

For your third generation iPad Pro, to connect to your TV via HDMI, you will need a suitable adapter and a good quality HDMI 2 (or better) cable.

Of available adapters, this one is from Apple:

• USB-C Digital AV Multiport Adapter

https://store.apple.com/uk/xc/product/MUF82ZM/A

Connect iPad to a TV, projector, or monitor with a cable - Apple Support