Sorry - It's Not possible to change this.
Nikon took a decision that this 100% zoom functionality was/is not needed on the non-pro bodies,,, D7000 has the same lack of 100% zoom.
You need to buy a new body, to the top of the line, to solve this.
It's back on the D7100 with three choices for magnification, though the percentage is not specified. (but it appears that "medium" is 100 percent)
I think it's present also on the D7200 but have not checked. The manual only shows that some option exists but not what it is, so I will have to find my wife's D7200 to check it.
edit to add: yes, it's on the D7200 too, and the percentages are shown also (medium is 1:1). The D7200 manual is about half the format size of the D7100, and they apparently had to save ink, but at least they did not stint so much on pixels!
A final edit to add: I just looked up the D7500, and it's there too. The menu item has moved from F1 to F2.