Agenda is the notebook for a plan , even if it was a personal one مذكرة has different meanings depending the context the one you need now is مذكرات muthak-karat =Diary (ies). we often use it in its plural form for it has entries for each day.

يوميات أجندة notes you take or write everyday.

أجندة = schedule مذكرة يومية = diary