We bought a dresser and we were given extra small wooden pieces and were missing longer wooden boards to complete the dresser.

Call them, they're extremely helpful. You probably missed one of the boxes. The boxes should have a 1, 2 etc.. in yellow indicating which box this is.

Ikea generally had great customer service, in person atleast. If you are unable to get what you need to happen online/over the phone, just come in in person. Last time I was there for something similar and it was easy breezy.