How do I get my calculator reloaded in my control center

Hello,

It sounds like you deleted the calculator app. Here's the steps to redownload the app:

Restore a built-in app that you removed

1. Go to the App Store.
2. Search for the app. Make sure that you use the exact name of the app. Find the correct name of built-in apps.
3. Tap to restore the app.
4. Wait for the app to restore, then open it from your Home screen.

This is taken from this article:

Remove built-in Apple apps from the Home screen on your iOS device with iOS 10 - Apple Support

How to reload the app back