Replacing keycode by UI Buttons doesn't work

I have tried everything but it still doesn't work. I am not talking about implementing functions wich has stuff inside when you click the UI Button. I want literally replace this Input.GetKeyDown(KeyCode.E). That is inside an if statement and replace with the UI Button object. How can i do this? I have tried with GetButton, GetButtonDown, trying to give a name and with Input.touchCount>0

I am developing a game like Resident Evil old style and when you enter a triggerStay and push the button, a text is showing up.

The Script

using System.Collections;
using System.Collections.Generic;
using UnityEngine.UI;
using UnityEngine.EventSystems;
using UnityEngine;

public class readingNote : MonoBehaviour {


    public AudioSource audio;
    public AudioClip collectSound;
    public  bool playerNextToKey = false;
    bool hasCollided = false;
    public GameObject pic;
    public GameObject text;
    public GameObject notePad;

    public Button yourButton;

    void Start()
    {
        pic.SetActive(false);
        text.SetActive (false);
        Button btn = yourButton.GetComponent<Button>();
        btn.onClick.AddListener(TaskOnClick);
    }

    void TaskOnClick()
    {
/*THIS IS SHOWING ALL TEXT IN THE SCENE AND NOT ONE BY ONE WHEN PRESSING*/
//      text.SetActive (true);
//      pic.SetActive(true);
    }

    void OnTriggerStay ( Collider other) {


        if(other.gameObject.tag == "Player") {
            if(Input.GetKeyDown(KeyCode.E)) {
            //if(Input.touchCount>0) {
                text.SetActive (true);
                pic.SetActive(true);

                AudioSource.PlayClipAtPoint(collectSound, transform.position);  

            }   

        }
    }


    void  OnTriggerExit ( Collider other  )
    {
        if (other.gameObject.tag == "Player")
        {
            //enter = false;
            //print("close");

            playerNextToKey = false;
            hasCollided = false;
            pic.SetActive(false);
            text.SetActive (false);

        }
    }

}