If I had to guess, I'd say probably 5,000 ships, because it was said to have been so big that it blackened the sea like a giant Archipelago. Estimation on how many or if Tolkien gives an exact number - any guesstimates?
Tolkien describes the fleet as being
like an archipelago of a thousand islands
-- Akallabêth, 4th part of The Silmarillion
Assuming this simile is anywhere near accurate, the Armament contained somewhere on the scale of a thousand ships - say roughly between 500 and 2000. Anything much less than 500, and it would instead be "like an archipelago of hundreds of islands"; anything much more than 2000, and it would be "like an archipelago of thousands of islands".
There's an interesting discussion here of how many ships and troops might have been in the Great Armament and how powerful it would have been.
If a man needs about 9 square feet (3x3 feet) to stand and have room to fight and there are 27,878,400 square feet in a square mile, there is room for about 3,097,600 warriors in a square mile. And in the War of Wrath Morgoth's troops filled the Plain of Angfauglith which could not contain their numbers.
And I guess that the Plain of Angfauglith could have been about 100 by 300 miles in size. And thus Morgoth might have had more than 30,000 times 3,000,000 soldiers in his army. Or 90,000,000,000. Thus the host of Valinor might have killed many times more Orcs than all the human soldiers and warriors who were ever killed in battle - plus all the ones who survived - in all of history!
So I picture the first ranks of the host of Valinor fighting and killing the first rank of the orcs, and then the second rank, and then the third,and so on and so on until they were tired, and replaced by the second rank in the host of Valinor, who would slay rank after rank of the orcs, and then they would be replaced by the third rank of the Host of Valinor,and so on, with the earlier ranks resting and eating and sleeping until it was their turn again.
And Morgoth would send more and more hastily born, raised, trained, and armed orcs to replenish his ranks, but the elves and maiar slew the orcs faster than they could be replaced and moved farther and farther toward Angband every day and every year until Morgoth finally totally ran out of orcs.
And if Sauron ruled an area in Mordor and farther east in the Second Age that, for example, totaled 1,000 miles by 1,000 miles, or 1,000,000 square miles, he might have taught his subjects advanced agricultural techniques so that they could have a population density of 100 per square mile and a total population of 100,000,000. And if they could send one percent of their population to war, Sauron could assemble an army of 1,000,000 warriors to resist Ar-Pharazon's invasion of Middle-Earth. But Ar-Pharazon's invasion force was so vast that it scared Sauron's army away.
So if this reasoning is correct Ar-Pharazon's force to invade Valinor, allegedly the greatest armament ever in Tolkien's history, could have been fantasticaly numerous, whether they all came from Numenor or not.