Is it possible to find an App for the IPhone? Does it exist?

[StephenG1CMZ]

Partly because of the loss of the Android HP Prime app on Android, I might migrate to an Apple iPhone.
I am unfamiliar with Apple, but I gather their equivalent of Google Play might be Apple ITunes.

A quick dive into Apple ITunes and selecting IPhone gave a screen trying to lure me into buying an IPhone, rather than an expected list of apps and a search button. (I'm accessing it from Google Chrome, as the IPhone arrived without SIM or USB power).

I'll keep hunting, but perhaps someone can confirm:
Can you look for apps before buying an IPhone?
Is ITunes the place to look? (the blurb mentioned tunes and podcasts, not apps).
How?
And does the HP Prime App still exist there?