在英语中，持续几天的时间可以用"for (duration) days"来表示。其中，"(duration)"表示时间的数量，可以是数字，也可以是"a few," "several," "many," "most," "all," "some," 等表示数量的形容词。

例如：

"I will be on vacation for two weeks." (我将休假两周。)
"The conference will last for three days." (会议将持续三天。)
"I have been sick for a few days." (我已经生病了几天了。)
"The storm is expected to continue for several more hours." (预计风暴将持续几个小时。)

来源：这是英语的基本语法，"for"是英语中表示时间的常用介词。

希望这对你有帮助！