the power points are the offensive or defensive power a unit has

if a Hoplite has a power point worth 10 then you would have to destroy 50 hoplites to gain the 500 power points as an example 

It's written in the units descriptions.

Attack power is unique.

Defensse power is variable, depending or your own offense main kind (expressed in total offense points por each kind, so you can compare them and determine which one is a majority).

Emm I don't think that's it, I had the same task yesterday and killing tenths of light soldiers got me 60 points only...

I meant how to determine the power point of a unit. I have subsequently been told that "divide the average defense or offensive strength of the unit by 40.  For example is a sword has avg. attack strength of 40/40=1 power point, jav avg. defense is 19/40= .475 power point.