How do I download latest compatible version of an app?
You need to update your iOS version, if possible, or live without those apps.  

As of iOS 11, Apple has told developers they must update their apps to 64-bit.  Older, 32-bit, apps can't be on the App Store anymore.

If you're on any version older than iOS 11 and the developer hasn't updated their app (it's the developer's responsibility to do this, not Apple's), you will not be able to download or run the app.