You would include your income on Schedule C, Profit or Loss from Business. You will also include your costs on the same form. The income is all one lump sum from your 1099-K. You can include one lump sum of the purchases under Inventory. You would include how much they originally cost, not the face value at the time of sale.
If you have other expenses related to the income, you can include these on the line that it pertains to.
