In which Fairy Tail Episode did Wendy Marvell first wear this beautiful dress? And where online can I get a Wendy Marvell Cosplay of her in this dress?

I realm wanna know what Episode it is that Wendy Marvell first wear this beautiful dress. And please can anyone give me links and website names to where I can go to buy a Wendy Marvell Cosplay in this dress from the picture? Thank you for all your help in advance :)