How can i get random 10 call numbers to be generated in this format = 005.73 JAM

How can i get random 10 call numbers to be generated in this format

• 005.73 JAM- In c# windows form

i tried this but i wanted to know how i can join generated string and number with decimal

 const string src = "abcdefghijklmnopqrstuvwxyz0123456789";
        int length = 9;
        var sb = new StringBuilder();
        Random RNG = new Random();
        for (var i = 0; i < length; i++)
        {
            var c = src[RNG.Next(0, src.Length)];
            sb.Append(c);
        }
        MessageBox.Show(sb.ToString());