Copy Data from one Sqlite table to another Sqlite table

I need to copy data from one Sqlite table to another. I wrote method, which return DataTable:

public static DataTable GetDataFromSecondTable(string filePath)
    {
        DataTable DbTable = new DataTable("Messages");
        using (var connection = new SQLiteConnection(filePath))
        {
            string SelectQuery = "SELECT * FROM Messages";
            using (SQLiteCommand cmd = new SQLiteCommand(SelectQuery, connection))
            {
                connection.Open();         

                using (SQLiteDataAdapter adapter = new SQLiteDataAdapter(cmd))
                {
                    adapter.Fill(DbTable);                        
                }
            }
        }
        return DbTable;
    }

Then I need to insert this DataTable to my "main" table, which has same structure:

public static void MergeData(string mainDbPath, string secondDbPath)
    {
        DataTable secondTable = GetDataFromSecondTable(secondDbPath);

        using(SQLiteConnection connect = new SQLiteConnection(mainDbPath))
        {
            connect.Open();
            using (var cmd = new SQLiteCommand(connect))
            {
                using (var transaction = connect.BeginTransaction())
                { 
                    foreach(DataColumn column in secondTable.Columns)
                    {
                        foreach(DataRow row in secondTable.Rows)
                        {                                
                            //cmd.CommandText = String.Format("INSERT INTO Messages ('{0}') VALUES('{1}')", column.ColumnName, row);                              
                            cmd.ExecuteNonQuery();
                        }
                    }

                    transaction.Commit();
                }
            }
        }

    }

I don't understand how I should set rows and columns to SQLite query. Maybe someone have another solution for this task.