This is what I got so far!

Code:
#include <iostream>
#include <fstream>
#include <iomanip>
#include <functional>
#include <algorithm>
#include <string>
#include <cstdlib>
#include <sstream>
using namespace std;

//Car Class
class Car
{
protected:
    string make;  //make
    string model; // model
    string color;  // color
    int year;  // year
    int mileage;  // miles on car
	int IntStackSize;
	int top;	//top of stack

public:
        //Constructor that will set information for a new car
        void New_vehicle (string a, string b, string c, int d, int e) 
        {make = a; model = b; color = c; year = d; mileage = e;}
        
        Car(); //Default constructor
        Car(string, string, string, int, int);
		//Stack Information
	
		void push(int);
		void pop(int &);
		bool isFull();
		bool isEmpty();

        //mutator and accessor functions
        void setMake(string);
	    void setModel(string);
	    void setColor(string);
	    void setYear(int);
	    void setMileage(int);

	    string getMake();
	    string getModel();
	    string getColor();
	    int getYear();
	    int getMileage();

	        //Check mileage to see if valid
	    void valid_mileage(int);
	    void car_details();
	    string string_car_details();
	


};

//Sets to default values
Car::Car() {
        make = " ";
    model = " ";
    color = " ";
    year = 0;
    mileage = 0;
}
        // My Vehicle set up(Make, model, color, year, mileage)
Car::Car(string make, string model, string color, int year, int mileage) {
    this->make =  make;
    this->model = model;
    this->color = color;
    this->year = year;
    valid_mileage(mileage);
}


void Car::setMake(string make) {
    Car::make = make;
}

void Car::setModel(string model) {
    Car::model = model;
}

void Car::setColor(string color) {
    Car::color = color;
}

void Car::setYear(int year) {
    Car::year = year;
}

void Car::setMileage(int mileage) {
    valid_mileage(mileage);
}


string Car::getMake() {
    return make;
}
string Car::getModel() {
    return model;
}
string Car::getColor() {
    return color;
}
int Car::getYear() {
    return year;
}
int Car::getMileage() {
    return mileage;
}


void Car::valid_mileage(int mileage) {
    if (mileage>=0)
        Car::mileage=mileage;
    else {
        Car::mileage=0;
        cout << "WARNING! You have entered invalid mileage!\n";
        }
    }

        void Car::car_details() {
            cout << "The current car is a " << year << ' ' << color << ' '
                        << make << ' ' << model << " with " << mileage << " miles.\n\n";
        }



        string Car::string_car_details() {
            stringstream buf;
            buf << "The current car is a " << year << ' ' << color << ' '
            << make << ' ' << model << " with " << mileage << " miles.\n\n";
            return buf.str();
        }
Code:
#include "CarClass.h"
using namespace std;

Car::Car(string make, string model, string color, int year, int mileage)
{
	const int SIZE = 6;
	Car Car_array[SIZE] = { Car("Porsche", "911", "Silver", 2005, 45000), 
                                Car("Ford", "Mustang", "Red", 2007, 12600),
                                Car("Voltzwagon", "Jetta", "Black", 2006, 20218),
                                Car("Jeep", "Cherokee", "White", 2000, 98322),
                                Car("Nissan", "Sentra", "Red", 2002, 76046),
                                Car("Voltzwagon", "Beetle", "Black", 2005, 28031)};
	top =-1;

}

//Set up Stack Push
void Car::push(int num)
{
	if (isFull())
	{
		cout << "The Stack is Full!\n";
		exit(1);
	}
	else
	{
		top++;
		Car_array[top] = num;
	}
}

//Set up Stack Pop
void Car::pop(int &num)
{
	if (isEmpty())
	{
		cout << "The Stack is Empty!\n";
		exit(1);
	}
	else
	{
		num = Car_array[top];
		top--;
	}
}

bool Car::isFull()
{
	if (top == IntStackSize -1)
		return true;
	else
		return false;
}
bool Car::isEmpty()
{
	if (top == -1)
		return true;
	else
		return false;
}

int main() {