Is there any rule about eating a parve food from a restaurant that serves both fish and meat?
If the food is from the meaty section, the food should not be eaten with dairy, as there might be residue of meat on it, or it may have been cooked in a meaty pot. However, if the food is from the fish section, there obviously is not any meat residue on it and I assume they have different pots for meat and fish.
Either way, you do not have to wait 6 hours between the parve food and dairy.
All the best
Regarding waiting 6 hours, see Rav Akiva Eiger Y:D 89