You'll need to use a power inverter like this one to power the unit: https://www.amazon.com/Foval-Power-Inverter-Converter-Charger/dp/B01H2XD2DY/ref=sr_1_15?s=automotive&ie=UTF8&qid=1508527273&sr=1-15&keywords=power+inverter
And as for a HDMI to RCA converter: https://www.amazon.com/Tendak-Converter-Composite-Convertor-Supports/dp/B01FX1ZWXK/ref=sr_1_2_sspa?ie=UTF8&qid=1508527612&sr=8-2-spons&keywords=HDMI%2Bto%2BRCA&refinements=p_72%3A2661618011&th=1
It does require USB power, which the Apple TV cannot provide. However, the power inverter does have USB outputs which you can use.
Hope this helps!