I would start by looking at the pricing for similar vehicles listed for sale by dealers on AutoTrader, CarGurus, etc.
And then I’d solicit several offers from the usual car-buying sources (Carvana, Carmax, etc.).
The private party market price is somewhere in between.
Where specifically to land on the asking price (closer to the upper or lower end of the range) will depend on how many tire kickers you’re willing to endure.