I don't think you have to have a prior version installed just have the serial number to enter when it askes for it.  Been awhile since I last did that, but when you enter the serial number and Poser sees that it is an upgrade it will enable the extra fields in the box to enter the older versions serial number.

Poser 5, 6, 7, 8, Poser Pro 9 (2012), 10 (2014), 11, 12, 13