Accessing Map Values Through A List

I am trying to create a method in BlueJ which needs the values from a Map to be copied into a List so I can use the List methods min() and max(). Here is the method I have created so far:

public String findNamesInPageRange()
{
int minOfRange = Integer.parseInt(OUDialog.request("Input number for start of range"));
int maxOfRange = Integer.parseInt(OUDialog.request("Input number for end of range"));
String foundIt = null;
for(String eachKey : bookIndex.keySet()) {
List<Integer> pageList = new ArrayList<>(); //Cannot access values from a map using this List
if((minOfRange >= Collections.min(pageList)) && (maxOfRange <= Collections.max(pageList))) {
foundIt = eachKey;
}
}
return foundIt;
}

As can be seen there is a comment showing where my problem lies.

The Map is coded as Map<String, Set<Integer>> bookIndex = new TreeMap<>();

Ive tried using bookIndex.values() as the argument of the List but I get an incompatible type error

So, how can this problem I am having be resolved?