If I exercise and lose 3500 cals, 1lb, in 1 day (not literally, it's just to simplify my question) how long will it take my 1lb lost to show on the scale if I don't exercise anymore that week?

So...I'm not sure if I quite understand what you mean...are you asking long it'd take for a 1 pound loss to show up on the scale? I'd have to say until it shows up on your scale as a 1 pound loss! So many things can factor into weight loss, kwim? Sodium, water, type of foods, exercise and the intensity of it, metabolic rate... Weight loss isn't always like clockwork. Although calories in vs. calories out is pretty right on!

I typically have a 1,000 calorie deficit at the end of each day, so that = a loss of 2 pounds a week. Monday is my official weigh in day, but sometimes when I weigh myself on the following Friday I can be the exact same weight as I was on Monday. Then the next Monday comes around and I'll be down 3 pounds. I obviously didn't "lose" the 3 pounds in 2 days, kwim? Then the next day I might be up .5 pound. Then nothing for a few days... But it's always going in the right direction as long as we're doing what we need to do!