By Taiga Uranaka and Ritsuko Shimizu TOKYO (Reuters) – The 81-year-old Japanese executive who built 7-Eleven into the worlds biggest convenience store chain has a new mission: turning more than 50,000 bricks and mortar stores in Japan into portals to a new online retail empire. To do it, Toshifumi Suzuki, the chief executive of department store to mail order retailer Seven I Holdings Co, is once again seeking inspiration in the United States. Its over 40 years since he kickstarted a revolution in Japanese retail by bringing 7-Eleven stores across the Pacific, eventually buying the U.S. owners after they sought bankruptcy protection. In Suzukis future vision, goods ordered online from Seven Is department stores and supermarkets, as well as outside partners, will be delivered to and picked up from the thousands of 7-Eleven stores spread across Japan at customers convenience.