。
This is my first proper vacation in three years.
Literal
Full-scale [attributive-な] vacation [topic-は] 3-years-[interval-ぶり] [is-だ].
~ぶり is a suffix meaning 'for the first time in X time' — 3年ぶり ('first time in 3 years'), 久しぶり ('long time no see,' literally 'first time in a long while'), 1週間ぶり ('first time in a week'). 本格的な vacation implies a proper, full vacation — not a short weekend getaway but an actual extended break. 休暇 is the formal/written word for 'vacation, leave' (more casual: 休み).