Just Google "Michelin RV Tire Guide"
It will give you recommended MINIMUM pressures for given weights.
Since you have only axle (vs individual wheel position) weights, suggest you add 5 PSI for left/right imbalance.
And another 5 PSI to that minimum to account for different loading (for example, when low on fuel (tank behind rear axle) the front axle will have more weight on it.
And, the more weight you can move forward, the better the handling and ride! Ideally, each axle will be loaded to the same percent of GAWR.