list a set of at least 12 numbers that has a minium of 28 maximum of 34 median of 30 mode of 29

28 x x x ... x x 34

Let's use 13 numbers. So, the 7th is 30
28 x x x x x 30 x x x x x 34

If we want integers, there aren't that many between 30 and 34, so some will have to be used at least twice. Let's make the mode (29) occur 4 times:

28 28 29 29 29 29 30 31 31 32 32 33 34