Is Apple Maps free? Is it on all iPhones and how do I access

Yes.

You can use Search to find it: Use Search on your iPhone, iPad, or iPod touch - Apple Support

Also note that if it is not on any home screen or in any folders on any home screen, if you have iOS 14, go to the App Library (swipe left past your last home screen). From there you can touch and hold an app and slide it left back to the home screen.

If none of the above helps, the app may have been deleted. To restore it, see the following from Delete built-in Apple apps from the Home screen on your iOS 14 or iPadOS device or Apple Watch - Apple Support

Restore a built-in app that you deleted

1. On your iOS or iPadOS device, 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.