1. I went to Shinsegae Department Store to buy some clothes.

2. I went to a Shinsegae Department Store to buy some clothes.

3. I went to the Shinsegae Department Store to buy some clothes.

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Which one is right? Don't we need to use the article before 'Shinsegae Department Store'?

Sentence 1 is best, I think. Sentence 2 means that there are many Shinsegae Department Stores and you went to one of them. Sentence 3 reads fine, too.