How many water molecules will form in process of dehydration synthesis?

Dehydration synthesis

NA, Avogadro's number, is the value of entities in one mole: 6.022*10+23

[998.2 gram / 18.0 g/mole] x 6.022 x 1023 = 334 molecules/Litre at 20oC

There is only one molecule of water in a water molecule.

both!