Your search for "One Piece Mini Case Set Vol. 3 Display Case" revealed the following:
It contains 2 booster packs, and a Promotion Card featuring 1 of 6 new designs! Contents・x12 mini tins per display・x1 Promotion Card per mini tin (6 types)・x2 Booster Pack [OP-17] per mini tin
It contains 2 booster packs, and a Promotion Card featuring 1 of 6 new designs! Contents・x6 mini tins ・x1 Promotion Card per mini tin (6 types)・x2 Booster Pack [OP-17] per mini tin