It's a size /8.
66% Polyester, 31% Cotton, 3% Elastane; Model Measurements: Height: 178cm (5'10'') Bust: 82cm (32in) Waist: 64cm (25in) Hips: 93cm (36in); The product on the model is S/36. Trendyol Navy Blue Corded Cotton T-shirt-Pants Knitted Pajama Set.