Complex sentence: Japanese author, who spent years tracking down the footprints in many Asian countries, estimates that he found over 3,000 such footprints, about 300 footprints in Japan and over 1,000 in Sri Lanka.
Split into simpler sentences: Japanese author, who spent years tracking down the footprints in many Asian countries, estimates that he found over 3,000 such footprints. There are about 300 footprints in Japan and over 1,000 in Sri Lanka.