Convert int to string and vice-versa

So I want to change this integer to a string, change a label’s text value and change it back to an integer. But I get these errors:

Assets/Scripts/Gun/Gun.cs(116,24): error CS0029: Cannot implicitly convert type`int' to `string'

Assets/Scripts/Gun/Gun.cs(117,24): error CS0029: Cannot implicitly convert type `int' to `string'

Assets/Scripts/Gun/Gun.cs(118,21): error CS1502: The best overloaded method match for `int.Parse(string)' has some invalid arguments

Assets/Scripts/Gun/Gun.cs(118,21): error CS1503: Argument `#1' cannot convert `int' expression to type `string'

Assets/Scripts/Gun/Gun.cs(119,21): error CS1502: The best overloaded method match for `int.Parse(string)' has some invalid arguments

Assets/Scripts/Gun/Gun.cs(119,21): error CS1503: Argument `#1' cannot convert `int' expression to type `string'

this is not the entire script:

	private int MAGBULLET;
	public GUIText AmmoUi;
	public GUIText VestUi;
	private int VESTBULLET;

	private void UpdateAmmoOnScreen()
	{
		MAGBULLET = magazineBullets;
		VESTBULLET = ammoInVest;
		MAGBULLET.ToString();
		VESTBULLET.ToString();
		AmmoUi.text = MAGBULLET;
		VestUi.text = VESTBULLET;
		int.Parse (MAGBULLET);
		int.Parse (VESTBULLET);
	}
}

ToString() returns a string.

int.Parse() returns an int,

string mb_string = MAGBULLET.ToString();
string vb_string = VESTBULLET.ToString();

AmmoUi.text = mb_string;
VestUi.text = vb_string;

int mb_int = int.Parse (mb_string);
int vb_int = int.Parse (vb_string);