If you already have a PDF of your return with all the worksheets, you can simply look for the forms I name below in that PDF. If you don't have such a PDF, you can open the return back up to view the forms.
If you prepared your return in desktop software (CD/download), here's how to see pages with the "effective tax rate." The pages are called "Filing Instructions" and "2018 Federal Tax Return Summary" (called "Return Summary" in the forms list.)
Launch TurboTax and open your return.
Once open, go into Forms Mode.
In the forms list in the left column, choose to view either or both of these forms:
Return Summary
Filing Instructions (1 or 2 pages). May be abbreviated as "Filing Inst."
Both of those forms are down near the bottom of the Federal portion of the left-column forms list.
NOTE: When you open your return, do not make any changes in it, since it has already been filed (I assume).
