@Kasie--Ha-0
I am afraid @Mike-And-Jane0 is right. Your guest cannot make a booking for the three nights he has already overstayed because you cannot book dates that have already passed.
It's really not an ideal situation, but I think you have the following options:
1. Get the guest to pay you directly. You shouldn't really do this according to Airbnb's T&Cs, but it might be the most straightforward way.
2. It the guest wants to continue his stay, you could ask him to make a new booking for the dates going forward and send him an alteration request for the nights he has already stayed and not paid for. However, you need to trust the guest in this circumstance and I am not sure this guest sounds trustworthy.
3. Get Airbnb involved. Tell them what has happened and see if they can charge the guest for overstaying. In theory, they should be able to do this, but in practice it could be a lot more complicated and there is no guarantee they will get the payment from him.
4. Do as @Mike-And-Jane0 suggests (providing it is within your legal right to do so). Tell the guest he has to pay or leave. If he does not, change the locks and give him a timeframe in which to collect his stuff. Make sure you have someone with you when he comes to collect it and be prepared to call the police if necessary.