en_tn/1ch/10/05.md

fell on his sword

He probably stuck the handle into the ground and leaned on the point so the sword would go through his body as he fell down. The action is a metonym for the result, death. See how you translated this in 1 Chronicles 10:4. AT: "killed himself with his sword" (See: rc://en/ta/man/translate/figs-metonymy)

his three sons

You may need to supply the words omitted by the ellipsis. AT: "his 3 sons died" (See: rc://en/ta/man/translate/figs-ellipsis and rc://en/ta/man/translate/translate-numbers)