How do you make gamepasses multiply the amount of points given?

To check if the player owns a certain pass, you can use the PlayerHasPass function. Now, instead of writing out the function call a bunch of times for each ID, you could implement a dictionary :)

Name your keys numerical values, corresponding to the desired multiplier. Have the values be the ID of pass needed to obtain said multiplier.

Then iterate through the array and check if the player owns the pass. If they do, pass the multiplier using string patterns.

local pService = game:GetService("GamePassService")
local vec3 = Vector3
local passes = { --Dictionary
	["Pass4"] = 1163402460,
	["Pass3"] = 1163401151,
	["Pass2"] = 1163394115
}

local function CheckForWalk(plr, hum, add) --Add parameter
	pcall(function()
		while wait() do
			if hum.MoveDirection ~= vec3.new(0, 0, 0) then
				while wait(5/plr.leaderstats["Steps"].Value^(1/2)) do
					if hum.MoveDirection ~= vec3.new(0, 0, 0) then
						--variable for readability
						local steps = plr.leaderstats.Steps
						steps.Value = steps.Value + add
					else
						break
					end
				end
			end
		end
	end)
end

game.Players.PlayerAdded:connect(function(plr)
	plr.CharacterAdded:Connect(function(char)
		local hum = char:WaitForChild("Humanoid")
		local add = 1;
		for i,v in next,passes do
			if pService:PlayerHasPass(plr, v) then
				--%d+ for numbers, tonumber to make it a number
				add = tonumber(i:match("%d+"))
				break
			end
		end
		CheckForWalk(plr, hum, add) --Pass multiplier to function
	end)
end)

######You should look into using a debounce