Reaching the Netherite Barrel
Get to Diamond or Obsidian first
Netherite Barrel sits above every other tier. You cannot craft it directly from wood or copper. Work up to Diamond Barrel using Wood To Diamond or the step-by-step tokens, or to Obsidian Barrel using Wood To Obsidian or Diamond To Obsidian. Either of those two barrels is a valid base for the final upgrade.
Apply the smithing transform
The Netherite Barrel is produced by the mod's single smithing_transform recipe. This is the only recipe in the mod that uses a smithing table rather than a crafting grid. Bring your Diamond Barrel or Obsidian Barrel to a smithing table along with the required smithing ingredients, and apply the transform to convert it into a Netherite Barrel.
Why it matters
Netherite Barrel is the largest and most durable storage option in the set. Because the smithing step consumes the base barrel, empty it before you begin. If you are still deciding between Crystal Barrel and Obsidian Barrel, note that Obsidian is one of the two valid Netherite bases, so choosing Obsidian earlier keeps the Netherite route open without an extra conversion. Crystal Barrel is a separate branch and does not lead to Netherite through the listed tokens.