Is not USB?

So I need an dedicated connector from TB3 to HDMI/Serial to project from a Macbook Pro?

TB3 and USB are different things. I know nothing of Macs but I expect a HDMI adapter is exactly what you need. A quick Google would suggest you can get one for under a tenner.

Yes you need either a cable or an adapter. The cable creation ones are good and support MacBook charging and seem to comply with connectivity protocols, not all adapters or cables are created equal.
If you need more connectivity then get a small dock thingy.

It is USB-C

It is USB-C

It is, but it’s also thunderbolt-3 which happens to share the same port. Not every USB-3 port or cable can support thunderbolt-3

https://www.cnet.com/uk/how-to/usb-type-c-thunderbolt-3-one-cable-to-connect-them-all/

You should be able to plug a USB-C device into a thunderbolt 3 socket.

It won’t fit in a thunderbolt 2 socket (it’s mini display port, not USB-C).