https://www.polygon.com/fortnite/2018/7/23/17602412/fortnite-founders-pack-skins-battle-royale

The Fortnite founder’s pack was originally released last year, on July 25, as the easiest way to buy Fortnite Save the World. A few months later, in September, when the game’s Battle Royale mode was released for free, fans who had previously bought the founder’s pack were promised skins for the new mode. But those skins never actually came out. Now after almost a year of waiting, Epic has announced the release of the two founder’s pack skins.

To thank you for your continued support, all founder's pack owners will receive the legendary Warpaint and Rose Team Leader Outfits in Battle Royale as part of our v5.10 release. pic.twitter.com/JhgswBdBZR