how to make bar-code label from encrypted text.

i am using USPS service. when i sent request for tracking label i got out put of encrypted text now i should make that encrypted text to bar code label.

I have tried following code but did not get any result. i C# (ASP.net) i am using

string str = "JVBERi0xLjINCjUgMCBvYmoNCjw8DQovVHlwZSAvWE9iamVjdA0KL1N1YnR5cGUg....";
        byte[] arr = System.Text.Encoding.ASCII.GetBytes(str);

        string strFileName = GetTempFolderName() + "yourfilename.gif";
        if (byteArrayIn != null)
        {
            using (MemoryStream stream = new MemoryStream(byteArrayIn))
            {
                newImage = System.Drawing.Image.FromStream(stream);

                newImage.Save(strFileName);

                Image11.Attributes.Add("src", strFileName);
            }

        } 

Please help me if you have any solution