How to save tables with datastore?

Making a ban function which is connected to a table but I don't know how to.

The Module Script

local banned = {} 

reason = "You have been banned from the game from a Developer"

local datastore = game:GetService('DataStoreService'):GetDataStore('MHARebornBanList') --The DataStore 
local banlist = {}--Storing the Banlist 
function banned.AddBanlist(userid)
	table.insert(#banlist, userid)
	local key = "Banned-"..userid
	local getsave = datastore:GetAsync(key)
	if getsave then
		
	end
end
return banned

For your use, I think instead of saving a consistent table, you should save separate keys to a Banlist datastore.

You have to use the SetAsync function to set the player's ID into a new key.

--Establish datastore
local datastore = game:GetService("DataStoreService"):GetDataStore("BanList")
local module = {}; --Declare module's environment

function module.AddBanlist(userid)
	local data = datastore:GetAsync(tostring(userid))
	if not data then --If they're not already there
		datastore:SetAsync(tostring(userid),true) --Add them
	end
end

--Usage
module.AddBanlist(69913657);