Where is the Downloads folder on iPad Pro

Unless Chrome has its own download area that you can save to, that file is probably lost in Chrome’s cache.

There are other third party Web browsers that support downloading and storage of content.

The one I use is called Perfect Web Browser.

New, all iOS 11 version here.

Perfect® Web Browser Pro by AppSimply

https://itunes.apple.com/us/app/perfect-web-browser-pro/id1360915927?mt=8

Here is the older, no longer supported, legacy version, last updated in April 2018.

Perfect® Browser+ (Legacy) by AppSimply

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

Good Luck to You!

Unless you saved it to an app that supports .dmg files it's likely to only be in chrome's cache. Can you not download it directly on the Mac that you want to install it on ?