Huh?
I have now received letters to vacate the property on oct. 14 .
Received from whom (the executor of the estate)? When did you receive these letters? I assume you have no written lease that governs your occupancy of your sister's home. Correct? Have you been paying rent to her estate? If not, why not?
I don't want the house I just want till dec. to find a place to move. What do I need to do to fight this oct. 14 date
First of all, October 14, 2018 is a Sunday, so nothing's going to happen on that date.
It sounds to me like, shortly before she died, your sister made a new will. You said her old will leaves her entire estate to you, but you didn't tell us what the new will says. It also sounds you've been living rent-free for the last ten months or so. Finally, I think it's safe to assume that someone other than you was appointed as executor of the estate. Under those circumstances, I would think that the best way to buy another couple months in the home would be -- quite literally -- to buy the time (i.e., to pay rent). Of course, the executor doesn't have to accept your offer.
Beyond that, if the judge thinks that there's a legitimate basis to challenge the validity of the new will, he/she might be willing to stay the eviction. However, it's now October 10, so the date mentioned is four days away. You're going to need to consult with a local attorney ASAP.