Where do I put total of all inventory cost?

I have already filed my taxes. I may have to amend if I should have reported total cost of all inventory rather sold or not? On schedule C Part 3 cost of goods # 33 I have cost check # 34 was there any change in determining quantities, cost, or valuations between opening and closing inventory? I checked no. Not sure if that is right? # 35 Inventory at beginning of year I put zero and explained I started my online ebay selling Jan 1. 2019. My question is 36a purchases I only put the amount that I paid for the inventory I sold. How do you get carry forward inventory where should I have put total amount, I paid for all inventory rather sold or not?