The Lufthansa Worldshops are outside security. Are you looking for hand luggage? Otherwise you would need to check you new suite case in at FRA. The World Shop in Terminal 1 B is pretty new and supposedly the larger one. It is on the depature level outside of security.

When you arrive at the B concourse just follow the signs to baggage claim. After leaving the secure area you should reach a large center hall where escalators go down to the baggage claim. Don't follow the escalators. Instead stay on the level and turn right 180° and walk towards security. The Lufthansa Shop should be on the right side.

Map with location of shop