adapters necessary in China for US-purchased tablet

What adapters (plug and voltage) do I need to be able to use my US-purchased Kindle Fire HD (computer tablet) in China? (I get different answers from almost every store I've asked in S. Korea.) Do you have suggestions for where to buy in Incheon, S. Korea? ...Seoul? ...Beijing?
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Will these be the same as I will need in South Korea? ...North Korea?
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Thanks.