How do I find week numbers in Agenda?
For Agenda v4 and above
Go to the settings of Agenda, then Date & Time, and toggle "Week Numbers" to on. The week number will then display in the top section of the day view.
For Agenda v3 and below
On the iPhone, week numbers are available in the landscape week view. Go to the week list view and rotate the device into landscape…you'll find it in the top right corner. On the iPad, they are available in the month, on the first day of the week.