You should be able to export them from BeerSmith 2 to a BSMX file, then open that in BeerSmith 3 and copy/paste them over to your Styles profile table. You probably need to go into Options->Brewing first and set it to display all style guides.
However in some ways this may work better with BeerSmith 3 which lets you select multiple style guides to display where BeerSmith 2 only allowed one at a time.
Brad