Get sys_file_reference by UID

$fileRepository = GeneralUtility::makeInstance(\TYPO3\CMS\Core\Resource\FileRepository::class);
$fileObjects = $fileRepository->findByRelation('fe_users', 'image', $user['uid']);
$image_1 = $fileObjects[0]->getIdentifier();

$pageUid = 123;
$fileRepository = \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance('TYPO3\\CMS\\Core\\Resource\\FileRepository');
$fileObjects = $fileRepository->findByRelation('pages', 'media', $pageUid);
$files = [];

foreach ($fileObjects as $fileObject) {
    array_push($files, $fileObject->getIdentifier());
}