I accidentally deleted my IMessages now when I try to download it on the App Store I typed in “IMessages” and I have not found the app

iMessage is Apple communication service.

Note: To send SMS/MMS and iMessages, the Messages app is used and it cannot be deleted.

Try searching for it => Use iPhone to search - Apple Support

You can try the app library route.

Swipe the screen towards the right until you see the app library, Search for Messages, Press and Hold the Messages icon, drag and drop it towards the left of the screen. Once the home screen appears the app should be appear.

You could try this and see if this will work because the messages app cannot be deleted.

Settings > General > Reset > Reset Home Screen Layout