.KEEPSAFE File

The keepsafe file extension is related to a security app of the same name (KeepSafe) and used for the default folder on Android devices.

So it's actually appended to a folder, not single file. This folder seem to contain encrypted backup.

How to open:

You can access this folder only with KeepSafe app installed on your device.

How to convert:

A conversion is unlikely. But once you have encrypted the data, you can convert these to anything you like.