用介詞of。

"pick up"后面可以加很多不同的介詞，具體取決于你想要表達(dá)的意思。例如：
1. "pick up" + "the book" 表示“拿起書”。 2. "pick up" + "the bus" 表示“搭上公交車”。 3. "pick up" + "the phone" 表示“接電話”。 4. "pick up" + "the keys" 表示“拿鑰匙”。 5. "pick up" + "the bag" 表示“撿起包”。

After "pickup," the appropriate preposition often used in English to describe a casual pickup form of transportation is "up." Therefore, you might have an expression like "pick up," if referring to an instance where someone is picked up (e.g., a car picks a person up or someone is picked up by an elevator or escalator in a shop, etc.).
However, if you meant "pickup truck" or "pickup car," you wouldn't need an additional preposition following "pickup," since the word "pickup" is already acting as an adjective.
Ultimately, the exact term and context determine what preposition to use after "pickup."