First of all your constructor is wrong. That is not how you write a constructor, you pass some params to constructor and those will be assigned to your class variables. So in your case your constructor will be following,
Car(String carMake, int horsePower, String colour, String vehicleType, String interior, int topSpeed){
cm = carMake;
hp = horsePower;
col = colour;
vtype = vehicleType;
intr = interior;
ts = topSpeed;
}
And for the solution to your problem what you are looking for is overriding the toString method of the class car. which can be done as following.
@Override
public String toString()
{
StringBuilder sb = new StringBuilder();
sb.append("Car Make: ");
sb.append(cm);
sb.append("\n"); //You can use System.getProperty("line.separator") if you want to make it platform independent
sb.append("Car colour: ");
sb.append(col);
//You can append as many details of your class car this way.
//and finally just return the StringBuilder as String.
return sb.toString();
}