It doesn't matter how long you've held your provisional licence because it doesn't make a different when it comes to car insurance. A full driving licence is what makes the difference.
With just a provisional licence, you cannot get car insurance for 1 day. The minimum length of cover that is available to you is for 4 weeks.
Your best bet is to take driving lessons with an approved instructor and take his car for the practical test. If you want to take your own car, then you'll either have to take four weeks worth of provisional insurance or get your own car insurance policy (an annual contract with your provisional licence) which will provide adequate insurance cover for you.