Hello and thank you for entrusting me to assist you. My name is ***** ***** I will do everything I can to answer your question.
No, there is no legitimacy to this whatsoever, as Facebook and Powerball have no affiliation with each other and you would never receive any legitimate Powerball winnings notice through or connected with Facebook. You you have undoubtedly been targeted for is an advance fee scam, wherein victims are told about a financial windfall of some kind and then tricked into paying up front fees to collect their money. As a rule of thumb moving forward, you will NEVER be asked to pay a dime to collect legitimate lottery or sweepstakes winnings. Ever. Any legitimate costs and fees would simply be deducted from the money you have already won. It's not necessary to send money to get money.
In the next days or weeks, be on the look out for similar "too good to be true" loan solicitations, "sweepstakes" winnings, and similar windfall type offers. These will be further scams perpetrated by the same individual contacting you now under a different guise. Scammers love to double back on potential victims like this with "followup scams" in the hope that, though they couldn't trick you the first time, they will trick you the next.
In the mean time, you would be wise to immediately cease further contact with this scammer and report the matter to the local police and FBI field office. You can locate your local FBI field office here.
I just wanted to followup with you to make sure that you did not have any further questions or concerns. For some unknown reason, the experts are not always getting replies or ratings (which is how we get paid for our work) that the customer thinks have gone through. In your case I have not yet received either. If you are having technical difficulties with reading, replying or rating, please let me know so that I can inform the site administrator.
In any event, it was a pleasure assisting you and I would be glad to attempt to assist you further on this issue, or a new legal issue, if needed.
Very best wishes.