How to upgrade my world traveler backpack?

1. First, you need to make a basic traveler's backpack. The formula of synthesis is to put the leather in the first row of the 3x3 grid in the center of the workbench, and put a box in the first grid below.

Secondly, once you have a basic traveler's backpack, you can combine the backpack and the upgraded items of the workbench to get a bigger backpack.

Finally, once the upgraded traveler's backpack is successfully synthesized and placed on the character, you can carry things with more capacity.