So if you want for some reason to get a count for each of the entites in your DB, run this code and get some output for it
$entity_type_manager = \Drupal::service('entity_type.manager');
$definitions = $entity_type_manager->getDefinitions();
foreach ($definitions as $definition) {
$entity_type = $definition->getLabel();
$storage = $entity_type_manager->getStorage($definition->id());
if (get_class($definition) == 'Drupal\Core\Config\Entity\ConfigEntityType') {
$entities = $storage->loadMultiple();
$count = count($entities);
} else {
$query = $storage->getAggregateQuery();
$query->count();
$count = $query->execute();
}
print_r ($entity_type . ' ' . $count ."<br/>");
}