If you have core - you will get core 10
if you have Pro - you will get Pro 10
Not sure you can add Pro to 10 through add features with a 8 Pro pack.. (after the fact)
So as suggested - you upgrade your oem core..
reinstall oem factory core 8, add pro features - upgrade to 10 pro
takes all of a few extra minutes to use RecImg to create a customrefresh.wim which can then be use to reinstall any version of 8 or 10 to that PC