If the item is coming from China*, you should allow 30 days for delivery.
This is mail order. If you need something on a deadline, buy it locally.
So, if the item has not arrived by March 11, go to the Resolution Centre and open an Item Not Received dispute.
You will be refunded.
If the item turns up after the refund, you can return it on your own dime. Or you can refund the refund using Paypal's Send Money feature.
What you cannot do is keep the item without payment.
*From Europe, 10-15 days
From North America 20 days.