Unity_SceneUtils.css

using UnityEngine.SceneManagement;

namespace _MyScripts.Utils
{
    public static class SceneUtils
    {
        private static string NameFromIndex(int buildIndex)
        {
            var path = SceneUtility.GetScenePathByBuildIndex(buildIndex);
            var slash = path.LastIndexOf('/');
            var name = path.Substring(slash + 1);
            var dot = name.LastIndexOf('.');
            return name.Substring(0, dot);
        }

        public static int SceneIndexFromName(string sceneName)
        {
            for (var i = 0; i < SceneManager.sceneCountInBuildSettings; i++)
            {
                var testedScreen = NameFromIndex(i);
                if (testedScreen == sceneName)
                    return i;
            }

            return -1;
        }
    }
}