how to make a 1,000 coins is will be 1K coins?

so im trying to make a game that if you have a 1,000 coins it will be replaced to 1K coins

You will have to do something like this:

local coins = 8985923
local simplifyCoins = 0

if coins > 999999 then
	simplifyCoins = coins / 1000000
	-- coins above 999,999 will now show up in the format: 5.5
	simplifyCoins = math.floor(simplifyCoins * 100)/100
	--rounds number down to 2 decimal places
	simplifyCoins = tostring(simplifyCoins)
	-- turn it into a string
	print(simplifyCoins)
	print(simplifyCoins.."M")
	
elseif coins > 999 then
	simplifyCoins = coins / 1000
	--coins above 999 will now show up in the format: 5.5
	simplifyCoins = math.floor(simplifyCoins * 100)/100
	--rounds number to 2 decimal places
	simplifyCoins = tostring(simplifyCoins)
	-- turn it into a string
	print(simplifyCoins.."K")
end

Prints

--8.98
--8.98M

basically you just check to see how high coins is, then divide it by whatever place it falls on, then concatenate an "M" or "K".

[EDIT] I made it round down 2 decimal places to make it easier to read for the larger numbers. Also,I would put the repeated code inside of a function that is called within the if statements to avoid repeating the same code (that would be a lot of wasted lines if you went up to quintillions)