。
Mother sent me a boxed set of grapes.
Literal
Mother [subject-が] box-packed [gen-の] grapes [obj-を] sent-for-me (polite).
箱詰め is a verb-noun compound from 箱 ('box') + 詰める ('pack') = 'boxed,' 'packed in a box' — a common format for gift shipments in Japan, where carefully arranged boxed fruit (特に 桐箱入り) is a premium item. 箱詰めのぶどう attaches as a modifier with の. The benefactive ~てくれる keeps the focus on mother's care for the speaker.