App Store icon missing from iPhone

How to move apps and create folders on your iPhone, iPad, or iPod touch - Apple Support

It probably got hidden by mistake and is attached to another app in a folder...Open each app one at a time to see if it is hidden there...if you find it just drag it out.

1. If you do not fid it Reset Home Screen Layout: Go to Settings > General > Reset. Reset Home Screen Layout:

Return iPhone settings to their defaults - Apple Support

You need to disable the restrictions.

Settings > Screen Time > Content & Privacy Restrictions > iTunes and App Store Purchases > switch options to "Allow" here.

Note: Content & Privacy Restrictions must be enabled to make changes