where is decimal in numbers

The buttons on the toolbar are gone. Now you do it similarly to the other way you could set decimal places in Numbers 2.3. In 2.3 it was in the cell tab of the Inspector. Now it is in the cell tab of the format sidebar.

select the cell(s) you want to format then click the cell formatter on the top left

Version 3.0.1 has a customizable Toolbar, but decimal format isn't a tool that is available. It must be done as Wayne Illustrated.

Jerry