"I do not know where my watch is."
Translation:Ich weiß nicht, wo meine Uhr ist.
weiß and wissen are the same verb -- weiß is the first person singular and wissen is the infinitive (and some of the plurals). It has to do with knowing of facts, as I understand it. Kennen has more to do with knowing people, knowing places -- things that you wouldn't learn in school. "Ich kenne wo den besten Kuchen finden" (I know where to find the best cake).