Download google chrome with iOS 9.3

It appear that it has been dropped for iOS 9.3.5

Have you looked for it in the app store? It may only be available for iOS 10 or later - if so, then you simply will not be able to download an older version.

Here are a few third party web browsers that I know are STILL being updated and supported on iOS 9.

Perfect Web browser

iCab Mobile Web browser

Dolphin Web browser

Aloha Web browser

Maven Web browser

Maxthon Web browser

Opera Web Browser

Perfect Web Browser JUST had a very recent update to iOS 11, but their older, last version update is still available here and had its last older iOS update this past April 2018.

Perfect® Browser+ (Legacy) by AppSimply

https://itunes.apple.com/us/app/perfect-browser-legacy/id373916467?mt=8

Good Luck to You!