How to change the horizontal axis and legend in a bar chart?

It always beneficial when posting a question to also post a worksheet so we don't have to recreate any data.

Anyway, the legend is for the data itself, not the horizontal axis. That is in my understanding.

As far as the horizontal axis, you can control that thru the spearsheet. Not thru a format like you seems to be trying.

The horizontal axis is automatically using 1, 2, 3, 4, etc. because you are not controlling it. The data is. It's just creating an ordinal numbering system.