How do you check if there is more than one of an object?

I am currently trying to figure out how to check for more than one of the same object and how to get rid of extras. Does anyone know how to do this?

use #whatever:GetChildren() then if it's more than however many you want maybe use a for loop to do something like..

local things = whatever:GetChildren()
for i = 1,(#things - 1)in pairs(things) do wait() --leaving one of the objects
v:Destroy()
end

I'm pretty new though so there might be a better way :P