How to make the cash to be '1M' when the player has a cash value of "1,000,000"?

NO SNIP OF SCRIPTS AS I DONT KNOW HOW TO DO IT

I am trying to make a tycoon but I want the cash to be “1k” when the cash is “1000”, “1M” when the cash is “1,000,000” etc... I can't figure out how to do it and when they buy something that cost “100M”, their cash will be deducted accordingly.

function convert()
	if cash > 1000000 then
		cashHolder.Text = tostring(cash/1000000) .. "M"
	end
end

cashHolder is your textLabel for your cash, you get the cash by millions then divide it by millions in order to get how many millions you have.