Ui Canvas/Error CS0117

For a unity game group project my task at the moment is to find out the following: In the game the player will sooner or later find a picture (in this case a map) lying on a desk, and when clicking on the map it will become screen sized so you can look at it properly, and when clicking again the map should go back to it's place on the table. I wanna realize this by using a UI Canvas and the function OnMouseDown. I've been trying to figure it out but right now I have the error CS0117 saying sth does not contain a definition for renderMode.

 using UnityEngine;
 using System.Collections;
 
 public class MapDummy : MonoBehaviour {
     private Canvas canvas;
     
     void Start(){
         canvas = GetComponent<Canvas>(); 
     }
 void OnMouseDown()
 {
         if(MapDummy.renderMode == RenderMode.WorldSpace)
     {
             MapDummy.renderMode = RenderMode.ScreenSpaceOverlay;
     }
 }
 
 void Update()
 {
         if(MapDummy.renderMode != RenderMode.WorldSpace
        && Input.GetMouseButtonDown(0))
     {
             MapDummy.renderMode = RenderMode.WorldSpace;
     }
 }
 }

This is my code so far. Can anyone tell me what my mistake is? And maybe how I have to put the settings for the Canvas? Thanks!