Open up the App Store, but you don't go to the "Updates" tab anymore. Instead, tap on your circular profile icon, which will open up your Account page, then tap on "Purchased" from there.
On the next screen, it's just like it was before. There's the "All" tab to see everything you've ever purchased (even free apps) and "Not on this iPhone" for things you might want to redownload.
To redownload an app, just tap on the blue cloud icon next to it. If the icon is gray, that means you can't download it anymore either because it doesn't exist anymore in iTunes or because it's a 32-bit app that no longer works in iOS 11. To see which, tap on the app icon. If the page loads and says the app needs to be updated by the developer, it's still a 32-bit app. If the page goes to a white screen, it means the app is no longer available on iTunes.