I see this on Rock Auto, which suggests that a gasket is indeed part of the pan:
https://www.rockauto.com/en/catalog/ram,2017,1500,3.6l+v6,3435446,transmission-automatic,oil+pan+gasket,8612
Mopar one available for $20.
It could be that a little RTV could be added to the gasket surfaces, as well.