Complex sentence: After his parents died in Poland from plague, at age 13 he immigrated to America arriving in New York but was unable to proceed to the California goldfields because of his youth, and then Australia arriving in 1856.
Split into simpler sentences: After his parents died in Poland from plague, he immigrated at age 13 to America, arriving in New York. Not permitted to proceed to the California goldfields because of his youth, he then journeyed to Australia, arriving in 1856.