what Ian says is true.
but if you read the entirety of my initial reply, I do give some advice on how you may be able to get the product info into the power store data base:
look carefully at the structure of the power store products table, the column names and data types.
if you edit the structure of your existing products table to match the power store products table, it may work.
you may need to add columns or remove some that are not relevant to power store.
the key to success with this is matching the names and data types. It will take some patience, and experimentation to get it right. I would suggest making a back up before you start.