i am totally confused about this practice problem. what steps are required i feel it's so overwhelming where do i start.

At a grocery store oranges are piled to form a pyramid shape. the person who stacks the fruit has found that 18 by 26 oranges will fit in the bottom row. each successive row can can fit one less orange in both the length and width. if this pattern continues, how many oranges will there be in the pyramid? (it is important you know how many rows the pyramid will have.)