We don't know how long the total circuit is from distribution box to trailer inlet so advice on cord length and gauge is problematic. One of the better things you can buy for your RV'ing (and other household use) is a Kill-a-watt device. One side is connected to the power source and the KAW has a receptacle for the device needing power. Mine will measure amperage, voltage, and watts consumed. Handy thing to have around when there is a question of amounts of power needed and what is happening inside the copper wires.
FWIW, I power a table saw with a longer cord. I bought a length of 8 AWG and attached an industrial male plug to the cord. I've never measured the power consumed since it has never tripped a breaker or sagged under the biggest loads. I mention it as an example of how larger wire gauges can bring reliability to the application.