Yes, that's good so far.
Do the calculation and you get:
Then, round your value to the uncertainty that you got;
What would the uncertainty of this be...?
I measured 52 pieces of aluminum foil stacked on top of each other with a micrometer that measures to 0.01 mm, I found the width of the stacked pieces to be 0.84 mm. I think that means it would be (0.84 mm +/- <0.005 mm)/52 but I don't know where to go from there...