The triggered ability that creates the copies can itself be countered by anything that can counter a triggered ability. If it is countered, no copies will be put onto the stack.

Spells cast from zones other than a player's hand and spells that were countered or otherwise failed to resolve are counted by the storm ability.

The storm copies enter the battlefield one by one, followed by the original spell. Each of them enters the battlefield with a number of +1/+1 counters equal to the number of Oozes you control as it enters the battlefield. If you don't control any Oozes at the start, the first one enters with no counters, the second one enters with one counter, and so on.

The copies are put directly onto the stack. They aren't cast and won't be counted by other spells with storm cast later in the turn.

If a spell with storm has targets, you may choose new targets for any of the copies. You can make different choices for each copy.

A copy of a spell can be countered like any other spell, but it must be countered individually. Countering a spell with storm won't affect the copies.