I can't seem to find my calculator icon

Do you mean you can't find the Calculator app on your phone? Or you can't find the shortcut in the Control Center?

For the app:

• Have you looked on every page and in every folder?
• Have you searched for it using Spotlight? Put your finger on the screen on any homepage somewhere between the icons and pull down. Type calculator into the search box.
• Have you deleted the app: Remove built-in Apple apps from the Home screen on your iOS 10 device or Apple Watch - Apple Support

For Control Center:

See this article: Use and customize Control Center on your iPhone, iPad, and iPod touch - Apple Support

If I search for "Calculator", it's the very first one that appears. You should be able to recognize it by the round buttons and the brown and orange interface. Do NOT search for "Apple Calculator". That brings up all sorts of dreck.

I want to reinstall the calculator application - when I search the iStore it only shows third-party calculator applications - P.S. my iPhone uninstalled a bunch of applications on its own.

For me another calculator comes up first in my search - but your clue helped me realize which one was the one I wanted - thanks

I'm glad it helped!