How to save data to selected save slot

I make saveGame function and I have 6 slots for saving. How can I say, to which slot should I save data? Should I create variables for each of 6 slots ?

private int currentActiveSlot;
private int latestSaveSlot;

const int _numberOfSlots = 7;

string[] dateTime = new string[_numberOfSlots];
int[] actNumber = new int[_numberOfSlots];
int[] stepNumber = new int[_numberOfSlots];
int[] transformPositionX = new int[_numberOfSlots];
int[] transformPositionY = new int[_numberOfSlots];
int[] transformPositionZ = new int[_numberOfSlots];
int[] transformRotationX = new int[_numberOfSlots];
int[] transformRotationY = new int[_numberOfSlots];
int[] transformRotationZ = new int[_numberOfSlots];
int[] task1Completed = new int[_numberOfSlots];
int[] task2Completed = new int[_numberOfSlots];
int[] task3Completed = new int[_numberOfSlots];
int[] task4Completed = new int[_numberOfSlots];
int[] task5Completed = new int[_numberOfSlots];

void Start()
{
    latestSaveSlot = PlayerPrefs.GetInt("latestSaveSlot");
}

public void ButtonSave()
{
    // How to say, to which slot should I save?

    latestSaveSlot = currentActiveSlot;

    PlayerPrefs.SetString("date time", "");
    PlayerPrefs.SetInt("act number", 0);
    PlayerPrefs.SetInt("step number", 0);
    //..
    PlayerPrefs.SetInt("latestSaveSlot", latestSaveSlot);
    PlayerPrefs.SetString("sceneName", SceneManager.GetActiveScene().name);      
    PlayerPrefs.Save();

    dateTime[latestSaveSlot] = PlayerPrefs.GetString("date time");
}

public void ButtonLoad()
{
    dateTime[currentActiveSlot]  = PlayerPrefs.GetString("date time");
    actNumber[currentActiveSlot] = PlayerPrefs.GetInt("act number");
    stepNumber[currentActiveSlot] = PlayerPrefs.GetInt("step number");
    //..
}

I think you should just make a script which will create a file where it’ll save your settings and the name/location can be changed depending on which button you will click

There is a post on habrahabr.ru, which is describing your case exactly. They are using Serialization into XML, but it’s all in russian.

You can use google translate nonetheless, here is the link Сохранение игры в Unity3D / Habr