Yarn type, weight, its lengths/weight parameter does not matter! You can use any you have there.        
| my pumpkin is worked flat and seamed. Ø Size of the finished pumpkin is about 15-16cm.
You need: straight or circular needles 4 mm;  I used Cascadas 220 Yarn (100% Peruvian Highland Wool; Weight: 100g (3.5 oz);Approx. Yardage: 220 yds(200m)) total weight of the yarn for the rib part is about 30g, and for the blossom end and the stem is about 8g. Fiber-fill Stuffing weight is about 8-10g for this size pumpkin.