Question

The answer to the first question is 10 molds but the second part is hard, can anybody help me?

Answer 1

Of the 10 possible molds, only two can have a base that is a square.  That is, a base where the all 4 sides are equal.  In this case, you can make the molds:

1,1,28 ;  where the base is a 1x1 square with height 28 cm.
and
2,2,7  ; where the base is a 2x2 square with height 7 cm.