In order to transfer items properly you should determine if the fields match what is needed by the PowerStore. This will help you figure out how much can be transfered and what must be changed, removed, or edited.
You can take a look at the PowerStore demo and look at one of the products update page to get a feel for what values are used in PowerStore and how it compares with the existing store. Here is a link to the PowerStore page, the demo is on the right side:
powerstore/