‘Of these were the isles/coastlands of the nations divided. (These were the sons of Japheth) in their lands, everyone after his tongue, after their families, in their nations.'
The phrase in brackets would be expected, compare Genesis 10:20 and Genesis 10:31, but is not in the Hebrew text. It may well have dropped out in error in copying.
The ‘descendants' of Japheth are thus seen as having spread out over the islands and the coastal regions on both sides of the Great Sea, the Mediterranean. However not all the above were coastland areas. The description is general rather than specific, indicating general whereabouts. ‘Isles/coastlands' really indicates ‘those across the sea'.