查询了一下原句，您把句子抄写错误了，请看红色字体修改处，应该是“can”。

Convenience is also very important in modern life， so we buy packaged or canned food that can be transported from long distances and stored until we need it， first in the supermarket， and then at home.

这样这个句子就很好理解了，that can be transported from long distances and stored是定语从句。

您提出的第二个问题，packaged or canned前为什么不加系动词be，这是由于packaged or canned作定语，修饰food，package是及物动词意为“包装； 包装，捆扎”，can也可以作及物动词，意为“将…装入密封罐中保存”，用过去分词packaged or canned修饰food，说明food和这两个动词形成被动关系。既然是作定语，当然不能加系动词了。