a ModuleScript is a collection of functions and variables. Your UI should be handled from the LocalScript when Sure is clicked, then you can send a remote event to the server to do things on server-side, or call a function from ModuleScript that way.
The structure of your code should look like this.
-- Local Script
local moduleScript = require(SomeModule)
local yourUI = ...
local SureButton = yourUI.SureButton
local NoButton = yourUI.NoButton
SureButton.MouseButton1Click:Connect(function()
yourUI.Visible = false
moduleScript.Confirm() -- Run the function when 'Sure' is clicked.
end)
NoButton.MouseButton1Click:Connect(function()
yourUI.Visible = false
end)