。
We're going to some factory for a tour tomorrow, aren't we?
Literal
Tomorrow somewhere [possessive-の] factory [to-へ] inspection [purpose-に] go [explanatory-んです] [confirmation-よね].
んです is the explanatory extender (contracted from のです) — invites the listener to share/confirm the premise. よね stacks two particles: よ (assertion) + ね (confirmation), together forming 'it's X, right?' with a tone that seeks light agreement. どこか ('somewhere') + の + factory = 'some factory or other.' 見学 is a factory/museum-style visit for observation purposes.