For A Level English coursework, what edition of a classic book should I reference?

I'm struggling with how to reference classic books, because I've been told to put the year and location of publishing for book references, as well as the publishing company name. But do I base the year off the year the edition I was using was published, or the original publishing date? And the original publishing company, or the one who published my edition? (e.g. I'm studying a book released in the 1800s but the specific copy I have was published in the 2000s)