"In a couple of hours" is correct if it is from now. "a couple of hours later" is correct if it is in reference to another time.

For example:

Hotel guy: Check out is at 11am.
You: Acutally, I'd like to check out a couple of hours later. Is that possible?

Or when you come down to reception early on the day you are leaving to get a newspaper:

Hotel guy: Hello, sir. Would you like to check out?
You: Actually, I'd like to check out in a couple of hours. Can I get a paper?

Lots of Japanese speakers do not make this distinction in English. "In" always means "after now". "Later" means "after that time".

Matthew

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Matthew@Poligo.com
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