How do I highlight every 12th row?

I’ve looked at conditional formatting for every other row, but I’d like every 12th row for 360 rows. Thanks.

Hello

define a Conditional Formatting (Format -> Conditional -> Condition...) for range A1:AMJ360 and
Formula is MOD(ROW();12)=0 and apply a cell style with your desired highlighting:
(here:Highlighting)

See also: Highlight-Every-12th-Row.ods and study the Conditional Formatting using Format -> Conditional -> Manage...

Hope that helps.