See, Yahoo! Mail has a feature that allows you to import all of your Facebook Contacts. GMail (and Google+ proper) has always allowed for you to import all of your Yahoo! Mail contacts. This seems like more of a hassle than it actually is. See, I’m guessing that you have an old Yahoo! Mail account laying around—most of us used that service at one point in the past.
Simply head over to the Yahoo! Contacts and select to connect your account to Facebook and import those contacts.
The Google half is just a smidge little more iffy. You have to go to “Mail Settings” and then “Accounts and import.” Select to import the contacts from your now-merged Yahoo-Facebook address book.
Alternatively, you could get to that same dialogue from the “Circles” tab on G+.