How to use the functions of one script in another with unity

I have the following problem: I have a script in unity (C#) which establishes a connection with the database. It provides it alone, in a GameObject and it works without any problem for me by placing the method with the name Start , I can see the database records without any problem. The problem comes to me when I change the name of the method to Dbcontec and I try to call it in another script at the time of compiling, it generates an error. Below I leave the code of the scripts to see if they can help me.

Connection with the database.

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using System;
using System.Data;
using Mono.Data.Sqlite;

namespace Dbconection {
    public class Dbcnx : MonoBehaviour {

        public int Idrow;

        // Use this for initialization
        public void Dbcontec () {

            string conn = "URI=file:" + Application.dataPath + "/db_cuentos.s3db"; //Path to database.
            IDbConnection dbconn;
            dbconn = (IDbConnection) new SqliteConnection(conn);
            dbconn.Open(); //Open connection to the database.
            IDbCommand dbcmd = dbconn.CreateCommand();

            string sqlQuery = "SELECT * " + "FROM data_cuent Where id = '"+Idrow+"'";
            dbcmd.CommandText = sqlQuery;
            IDataReader reader = dbcmd.ExecuteReader();
            while (reader.Read())
            {
                int id = reader.GetInt32(0);
                string nombre = reader.GetString(1);
                //int rand = reader.GetInt32(2);

                Debug.Log( "id= "+id+"  nombre ="+nombre);
            }
            reader.Close();
            reader = null;
            dbcmd.Dispose();
            dbcmd = null;
            dbconn.Close();
            dbconn = null;

        }
    }

}

Script where I am calling the connection

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using Dbconection;

public class Inicio : MonoBehaviour {

    public Dbcnx dbcnx;
    public int Idrow;

    // Use this for initialization
    void Start () {
        dbcnx.Dbcontec();

    }
}

Error that is generated.

NullReferenceException: Object reference not set to an instance of an object Start.Start () (at Assets/Start.cs:13)