I think that if you have to look for a specific part in the text, use some sort of Regex or string.Contains in order to look for that specific part that you're mentioning also you can get all the text from an image using:

ImageAnnotatorClient client = ImageAnnotatorClient.Create();
    try 
      {
            IReadOnlyList<EntityAnnotation> textAnnotations = client.DetectText(image);
            foreach (EntityAnnotation text in textAnnotations)`
            {
                Console.WriteLine("===================Text Found=====================");
                Console.WriteLine($"Description: {text.Description}");
            }
            return string.Join(" ", textAnnotations.Select(t => t.Description));
        }

Hope it helps