The phrase "alone how many" is not correct and does not make sense in written English.
It seems to be an incomplete thought or question, and without additional context, it is unclear how it could be used.
Example: "I was wondering alone how many people would attend the event."
Alternatives: "by myself how many" or "just me how many".
In the past year alone, how many planes, alien spacecraft, and other solid bodies have exploded before our eyes?
It is hard to say how many of them are registered to vote, let alone how many actually show up at the polls.
Nor can the government of Nepal be expected to regulate how many climbers are on Everest, let alone how many go for the summit on a given day.
I don't even know how many place settings of good china I have, let alone how many people are coming for dinner this year.
On another day it would be the 26-year-old who was the story alone – how many unbeaten 150s get second billing, after all?
The country is so vast and roadless that no one knows, to the nearest million, how many people died in the war, let alone how many potential voters live there now.
God alone knows how many Incas were slaughtered by Pizarro.
But he will expand Medicaid anyway, and so save his state $227m next year alone.Exactly how many states will expand their Medicaid coverage is still unclear.
Ah, but it was devilishly hard to determine whether such a petition existed, let alone divine how many signatories it had.
The biggest financial rewards bear a flimsy relationship to talent, let alone desert: how many of the top 1% really contribute to the quality of life of the other 99%?
The lord alone knows how many military disasters (including many that have been concealed from us) have been the result of an inbred officer class that included many who were given the safe haven of a regiment to stop them creating chaos at home.
