Good afternoon melania130,
Welcome to the Apple Support Communities!
I understand you may have uninstalled an app on your iPhone. You would like to reinstall it and grant access for the app to use the mic and camera. What app are you referring to? If you update your iPhone to iOS 13.3, this will refresh all of the native apps. (Restart your iPhone after a software update). If you still can't find the app doing a search on your iPhone, then you can download and install it again. The first time you try to use the app, if it requests to use the mic or camera on your device, then the app will appear in the privacy settings. Here are some general resources to help you with this:
Remove apps from iPhone - iPhone User Guide - iOS 13
Use Search on your iPhone, iPad, or iPod touch
Redownload apps, music, movies, TV shows, and books
To manage which apps can access the camera or microphone on your iPhone, open the Settings app, tap Privacy, and then tap Camera or Microphone.
Apps that have requested access to the camera or mic will appear in a list. You can turn the switch on (green) or off (white) at any time.
Please reply to this thread with the additional information requested, and I'll do my best to help you with this!
Take care.