You are probably trying to place them in Program Files, which is no longer used since WinVista. You need the mIRC directory under Application Data.
Type //run $mircdir in mIRC to open the dir that contains settings files.
So then I just copy & paste my old mIRC.ini file into that mIRC Application Data folder and then it should work with the newest mIRC? Also, do I need to copy & paste my old mIRC.ini file into the 'backup' folder as well?