Your USB/HDMI ports are really there for connecting and mirroring your cell phone to the radio - doesn't really work that well.
You should have standard cigarette lighter power ports in both your dash as well as the laptop desk. The easiest thing to do is buy USB power ports into those:
Something as simple as this:
Or as big as this:
Or if you are into drilling holes in your dash and wiring to 12 volt systems you can buy something like this:
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