data = Table[RandomReal[],
 {i, 1, RandomInteger[{4, 8}]},
 {j, 1, RandomInteger[{4, 8}]},
 {k, 1, RandomInteger[{4, 8}]}
];

m = Max[data]
Position[data, m]

data = Table[RandomInteger[{1, 10}],
 {i, 1, RandomInteger[{4, 8}]},
 {j, 1, RandomInteger[{4, 8}]},
 {k, 1, RandomInteger[{4, 8}]}
];
m = Max[data]
Position[data, m]