This compares the grain to the sand of sea to emphasize its great quantity. Alternate translation: "The grain that Joseph stored was as plentiful as the sand on the seashore" (See: [[rc://en/ta/man/translate/figs-metaphor]])
Here "Joseph" and "he" stand for Joseph's servants. Alternate translation: "Joseph had his servants store up ... they stopped" (See: [[rc://en/ta/man/translate/figs-synecdoche]])