if all elements in daysList have same id then:-
List <MobileElement list = daysList.findElementsById("id");
if you just want to act on a particular element:-
daysList.findElementsById("id").get(index).click() / getText();
if each element in daysList have unique id then:-
daysList.findElementById("id").click() / getText();
You can't cast MobileElement object to ListView, MobileElement class is in Appium framework whearas ListView class is in AndroidFramework, both belongs to different entities.