I am not going to treat Genesis 46:8-27 as part of the Joseph story. In the Joseph story Benjamin is still very young. But, according to this list of the descendants of Jacob who went down to Egypt, Benjamin went down with 10 sons (vs. 21-22). This is a later genealogy.
The “he” in v. 28 refers back to Jacob in v. 7 or v. 5. The original story picked up in 28 and makes perfect sense following either of the earlier verses.
Joseph rides out in his chariot to meet the wagon train coming down from Beersheba. There is an emotional scene where Jacob meets Joseph after a quarter century of thinking him dead. The rest of the passage deals with Joseph’s clever plan to get Pharaoh to let the family settle in the land of Goshen. This was apparently the Wadi Tumilat, a grassy valley along a mostly dried-up branch of the Nile.
Joseph’s strategy is to emphasize that the Israelites are shepherds and cattle herders. Joseph knows this will cause Pharaoh to separate the Israelites from the Egyptians. Joseph supposedly knows that shepherds are “an abomination to the Egyptians.”
This reminds me of the claim in 43:32 that for Egyptians to eat together with Hebrews was “an abomination to the Egyptians.” Neither claim about what was taboo for Egyptians is confirmed by any Egyptian records.
Manetho (a later Egyptian historian whose writings we have only as they are quoted by other ancient historians) apparently referred to the Hyksos as “shepherd kings”. Maybe Egyptians feared that shepherds might usurp their kingdom again as the Hyksos had. But the Joseph story does not name the Pharaoh (although, one should look at the mention of the land of Rameses in 47:12), so we do not know what dynasty or period to think of as a historical setting for this. Manetho is a pretty shaky source anyway.
The exodus story requires that the Israelites have flocks and herds, but also be urban slaves. Egyptians would recruit agricultural workers to work on public works projects during the non-agricultural season after the Nile’s flooding receded. We don’t know how this would work for herders.
Both the visions of Jacob at Beersheba in 46:1-5 and the story of how Israel came to dwell in the land of Goshen in 46:31-47:12 help set up the exodus story. To what extent the details go back to pre-exodus sources, we cannot find out.