Both of your sentences are grammatically correct, although we don't use ''u" for ''you" in formal writing. Even though the grammar is correct, however, Americans usually use as few words as are necessary. There are a number of different ways to make that statement, I'd say, ''I forgot where you come from," or ''I forgot where you're from.'' "Forget" and ''forgot" would both be commonly heard in this type of statement.

Actually they're both wrong. Sorry. The correct way to say it is, "I forgot where you come from." If I were the one to say it, I'd say, "I forgot where you're from."

Oh well it'd say it's "I forget the place where u come from"....

thank you^^ :)

Please don't use "u" for "you" - it's not an acceptable habit in writing. Only the lazy write like that.