Open the App Store
Tap your profile icon in the top right
Tap Purchased
Tap My Purchases
Browse the list of apps you have downloaded before
Use the search bar to find the deleted app
Tap the download icon to reinstall it
Check the App Library by swiping left on the Home Screen
Use Spotlight Search by swiping down on the Home Screen and typing the app name
Check Screen Time > Content & Privacy Restrictions if the app is missing due to restrictions
Check Settings > General > iPhone Storage to see installed and recently removed app data
Check your purchase history in the App Store if you want to confirm the app was downloaded before