Format a cell like another

Format/Copy Style followed by Format/Paste Style

Or use the keyboard shorcuts for them (you will see them in the menu)

Or customize the toolbar and add those two icons to the toolbar so you can click on them. That's what I did.

I like shortcut keys. When they work.

Alt-Command-C (to copy the formatting), and Alt-Command -V (to paste formatting).

Shift-Alt-Command-V, pressed after copying a formula from a cell will paste the formula into the new cell, carrying THAT cells formatting.