I used the below method to change the detail viewcontroller navigation bar title to "Picture 1 of 10", for example.

I changed the Title property using Switch/Case method. Is it ok? attached screenshot link: https://drive.google.com/file/d/1E0814xrKI5hiN8rvv2hVDztWbHEL7UXx/view?usp=sharing

class DetailViewController: UIViewController {
    @IBOutlet var imageView: UIImageView!
    var selectedImage: String?

    override func viewDidLoad() {
        super.viewDidLoad()

        //change navigation bar title of picture page
        switch selectedImage{
        case "nssl0033.jpg":
            title = "Picture 1 of 10" //both are optionals so no need to unwrap
        case "nssl0034.jpg":
            title = "Picture 2 of 10" //both are optionals so no need to unwrap
        case "nssl0041.jpg":
            title = "Picture 3 of 10" //both are optionals so no need to unwrap
        case "nssl0042.jpg":
            title = "Picture 4 of 10" //both are optionals so no need to unwrap
        case "nssl0043.jpg":
            title = "Picture 5 of 10" //both are optionals so no need to unwrap
        case "nssl0045.jpg":
            title = "Picture 6 of 10" //both are optionals so no need to unwrap
        case "nssl0046.jpg":
            title = "Picture 7 of 10" //both are optionals so no need to unwrap
        case "nssl0049.jpg":
            title = "Picture 8 of 10" //both are optionals so no need to unwrap
        case "nssl0051.jpg":
            title = "Picture 9 of 10" //both are optionals so no need to unwrap
        case "nssl0091.jpg":
            title = "Picture 10 of 10" //both are optionals so no need to unwrap
        default:
            title = nil //both are optionals so no need to unwrap
        }

        navigationItem.largeTitleDisplayMode = .never

        // Do any additional setup after loading the view.
        if let imageToLoad = selectedImage{

            imageView.image = UIImage(named: imageToLoad)
        }
    }

Edit*:I also just solved using the recommended method by modifying from View Controller.