Actually I think the error says something more like "unable to convert from string to int", not label.
The problem is S7, you are storing it in a string, but in your query parameters you have it set as an Int.
Here are the two lines, notice how s7 is stored in a string, and parameterized as an int.
string s7= des.Text.ToString().Trim();
cmd.Parameters.Add("@t7", SqlDbType.Int).Value = s7;