different methods of loading level unity code example
Example: Change Level in Unity
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
}