Number + 届 + Event Noun
届 (jiè) is a measure word (classifier) used for scheduled events, sessions, or terms, such as the Olympics, congresses, or graduating classes. It is placed between a number and the event noun. For example, 两届奥运会 means 'two editions of the Olympic Games.'
这是第三十届校运动会。
zhè shì dì sānshí jiè xiào yùndònghuì.
This is the 30th school sports meet.
他参加了两届奥运会。
tā cānjiā le liǎng jiè àoyùnhuì.
He has participated in two Olympic Games.
我们这一届毕业生特别团结。
wǒmen zhè yī jiè bìyèshēng tèbié tuánjié.
Our graduating class is especially united.