How to display errors or messages from sqlserver to asp.net in try /catch blocks

create  PROCEDURE [dbo].[InsertDetails]
	
	@Cname varchar (50),
	@ImageName varchar (50),
	@imagepath varchar(50),
	@uploadedby varchar(50)
	
As
BEGIN
DECLARE @count INT
SET @count = (SELECT COUNT(*) FROM UUDetails)
IF @count >= 20

BEGIN
   PRINT 'You cannot insert more than 20 records'
   
END

ELSE
INSERT INTO UUDetails(UserName,ImageName,ImagePath,UploadedBy,UploadedDate)values(@Cname,@ImageName,@imagepath,@uploadedby,GETDATE() )

RETURN scope_Identity()
END

try
            {
              SqlConnection con;
              SqlCommand cmd;
              SqlParameter ret;
                        con = new SqlConnection(ConfigurationManager.ConnectionStrings["ConStr"].ConnectionString);
              FileUpload1.SaveAs(Server.MapPath("Images/" + filename));
              cmd = new SqlCommand("dbo.InsertDetails", con);
              cmd.CommandType = CommandType.StoredProcedure;
              ret = new SqlParameter("@RETURN_VALUE", SqlDbType.Int);
              ret.Direction = ParameterDirection.ReturnValue;
              cmd.Parameters.Add(ret);
              cmd.Parameters.Add("@Cname", SqlDbType.VarChar, 50).Value = txtcustname.Text;
              cmd.Parameters.Add("@ImageName", SqlDbType.VarChar, 50).Value = filename;
              
                            cmd.Parameters.Add("@Uploadedby", SqlDbType.VarChar, 50).Value = txtuploadedBy.Text;
              con.Open();
              cmd.ExecuteNonQuery();
             
                int j = Convert.ToInt32(ret.Value);
                con.Close();

                if (j >= 0)
                {
                  Label1.Text = "<b1>Record sucessfully Inserted</b1>";
                 gvCustomer.DataBind();
                
                }
                          }
              
            catch (SqlException ex)
            {
              Label1.Text =ex.Message;
            }
            catch(Exception  ex)
            {
              throw ex;
            }