Only one Dalek is required to block the equipped creature. Other Dalek and non-Dalek creatures may also block that creature and are free to block other creatures or not block at all.

If one creature is somehow equipped with multiple Ace's Baseball Bats, that creature still requires only a single Dalek to block it.

The defending player, not the attacking player, chooses which Dalek blocks the equipped creature.

If each Dalek that could block the equipped creature is tapped or is affected by a spell or ability that says it can't block, then none of them block. If there's a cost associated with having each of those creatures block, its controller isn't forced to pay the cost, so they don't have to block in that case either.