How do I tell the core what path to use if I move over the files?
To get it on SSD I will need to start fresh and tell it /appdata/blah blah blah
But if I move the files to c:/users/appdata how do I tell the core that?
Use -datadir command line option. e.g. bitcoin-qt -datadir=D:\Blockchain\BTC - or there is a registry setting you can change, but I'm not using windows right now to look for you.
NOTE: The -datadir command line option overrides the registry setting. You could run regedit and look for it. Something like HKEY_USERS_SOFTWARE/BitcoinCore or something like that. Look for a string which relates to the data directory.