How to copy Unity Game (SpaceFlight Simulator) from Galaxy S6 Edge to S9?
Summarizing from the comments on the question:

Helium does do the job if the actions are performed correctly:


Backing up the app on the source device
on the target device, copy the folder to the exact location to where Helium creates the backups
on the target device, restore the app.


If step #2 wasn't exactly followed, Helium wouldn't find the backups on the target device.

A comparable approach would be using adb backup (see our ADB tag wiki for details). To use that, you will need to know the package name of the app to deal with (that is e.g. what you find on the playstore URL by the "id" parameter). Then:


Connect the source device
Run adb backup -f foobar.ab -apk com.app.foobar¹
Disconnect the source device, connect the target device
Run adb restore foobar.ab¹


Another detail: you can mix the two approaches. Backups created by Helium contain that *.ab file, which you could pass to adb restore.



¹ of course replace foobar and com.app.foobar with the corresponding app name