This was their last exam — then on to graduation and jobs. 

【翻译】这是他们最后一次考试，然后就是毕业和工作。

then on to 这个说法正确。表示对某个事件的延续。意为“然后就......”。又如：

1. They were climbing up the wall of the house and then on to the branches of the tree. 

它们正在顺着房子的外墙往上爬，然后爬上树枝。

2. If you cherish their own, then on to his own choice. 如果你珍爱自己，那么就该重视自己所做的选择。

3. It started with cider, then on to wine and then on to vodka. 

一开始是苹果酒，接着换成了红酒，最后变成了伏特加。

4. He journeyed up the Volga and then on to St. Petersburg and western Europe. 他麦加起来伏尔加，然后对圣彼得堡和西欧。

5. I'm looking forward to tonight when we are going out for a meal with our bridesmaids and friends and then on to tomorrow. 

我很期待晚上和伴娘、朋友们一起吃饭，然后期待明天的婚礼。

A . E . port, then on to Saudi Arabia, ship.  

油轮报告称将前往阿联酋的另一个港口, 然后去往沙特.

Then on to chasing behind.  

追兵随后就来.

And then on to Katherine, sitting desolately, no sign of life except for her shallow breathing. 

然后去凯瑟琳屋, 她垂头丧气地坐着,除了浅弱的呼吸声外, 没有一点生机.

Tomorrow hopefully we will get to the desert and cross it. Then on to Urumqi!  

希望明天我们能到达真正的沙漠并穿越它! 然后向乌鲁木齐前进!