Here "the world" is a metonym for the people who live in the world. Alternate translation: "the people in the world" (See: [[rc://en/ta/man/translate/figs-metonymy]])
Paul asks this question to emphasize that when God accepts the Jews, it will be a wonderful thing. You can translate it in an active form. Alternate translation: "how will it be when God accepts them? It will be like they have come back to life from among the dead!" or "then when God accepts them, it will be like they have died and become alive again!" (See: [[rc://en/ta/man/translate/figs-rquestion]] and [[rc://en/ta/man/translate/figs-activepassive]])