Complex sentence: The number of Muslims in South Korea is estimated at about 30,000 mainly consisting of people who converted during the Korean War and their descendents and this figure doesn't including migrant workers from South and Southeast Asia.
Split into simpler sentences: The number of Muslims in South Korea is estimated at about 30,000, mainly consisting of people who converted during the Korean War and their descendents. This figure doesn't including migrant workers from South and Southeast Asia.