Disclaimer: Follow these steps at your own risk.

You could use an app back up program, copy it over to the Kindle Fire (maybe through a cloud service), and then install the app.

Example app back up program to .apk file type:

https://play.google.com/store/apps/details?id=mobi.infolife.appbackup

And then follow instructions like these to install an .apk file from an unknown/non the Play Store source:

https://www.androidauthority.com/how-to-install-apks-31494/

I should also note that the Miro tablet app may not run properly on a Kindle Fire, and Miro will likely not support it as the Kindle OS is not exactly “Android” - more on this here:

https://www.howtogeek.com/232973/amazons-fire-os-vs.-googles-android-whats-the-difference/

You could also try installing the Play Store app the Kindle Fire - again, do this at your own risk:

https://www.google.com/search?q=installing+play+store+on+fire+tablet