1. Run the below SOQL to get the PermissionSet Id.
SELECT Id, Profile.Name
FROM PermissionSet
WHERE Profile.Name = 'System Administrator'
2. Use the PermissionSet Id from the step 1 and use it in the below SOQL for ParentId.
SELECT Name
FROM ApexPage
WHERE Id IN (
SELECT SetupEntityId
FROM SetupEntityAccess
WHERE ParentId = '0PS4x000003oZ9DGAU'
AND SetupEntityType = 'ApexPage'
)