From my experience, most printers require a 1/4 inch (equals 18 points or 1p6) minimum from trim to any “live” copy. So if you place your page numbers 1/4 inch from trim to top of type, and 1/4 inch from outside trim, you’ll meet the requirement. As the page numbers change from single to triple digits, make sure that they expand toward the inside of the page, not outside toward trim. The left page should be set to left align, the right page should be set to right align
Design-wise, they might look better closer to the text. Your top margin is .75, if that is inches (you did not give units), it is 4p6 in picas, so your folios (page numbers) could nicely sit above at 2p6 for instance, and flush outside to align with the text below. That is a “normal” setup for book work (and usually there is a running head after the page number as well, for instance “chapter number” on the left page and “chapter title” on the right page. Not sure what your set up is.
hope this helps.