Check out example codes for "Change Level in Unity". It will help you in understanding the concepts better.

Code Example 1

public UnityEngine.UI.InputField sceneInputField; //Refence to your inputField

public void ChangeSceneBasedOnInputField() //Code that needs to be called
 {
      UnityEngine.SceneManagement.SceneManager.LoadScene(sceneInputField.text);  
     //This way you can type either the index of the scene or it's name
     //Will throw an error if it can`t find the scene
}

Code Example 2

SceneManager.LoadScene(scenename);

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