How can you configure a dealer with your own loot in Minecraft?

I need one of the lucky blocks sold. Can someone give me an order and explain what it means and how to change it practically?

/ summon villager ~ ~ ~ {VillagerData: {level: 99, profession: "minecraft: armorer"}, Offers: {Recipes: [{buy: {id: "minecraft: oak_boat", Count: 1b}, buyB: {id: "minecraft: birch_boat", Count: 1b}, sell: {id: "minecraft: gold_block", Count: 1b}}]}}

The oak boat is the first item he wants and the birch boat is the second item. The gold block is supposed to represent the lucky block.

If he only wants one item, you have to delete buyB: {id: "minecraft: birch_boat", Count: 1b}.