Terminating your instance is essentially deleting it, it will take some time to get reflected on your dashboard which essentially means that it won't appear on your instance list table. There is no use of terminated instances and once you terminate your instances, it means you have completely lost that particular instance.
But if during the time of the creation of your instance, you had enabled the option called Protect against accidental termination, then you will not be able to terminate without disabling this option.
But in your instance table if the Instance State column has the value terminated it means your instance is deleted and you can no longer use it.