Do not by the up grade. In fact you can get your money back for the (Daz3D - Millennium Boys
Daz3D - Millennium Girls) you have the full verison of Young teens and that will give you those figure also.

Down load the file again. Make sure poser is closed before you install and read the read me to see where the .exe put everything. I have the up-grade. Maybe the full version puts the figures in a different folder. Never hurts to check.

Look in your geometries folder and look in DAZpeople and see if there is an blYTGirlPT.obj. If so, the figures are ther and you just need to find the figures Cr2 in the figures folders.