Can I access data from an app that no longer works using iCloud backup?

I have an app on my phone that will no longer open. I’ve tried contacting the developer but gotten no response. Also tried installing the app on another device (iPad with same Apple ID) and while the app opens there, the data is blank. I imagine the data is stored on the iPhone itself and therefore would be included in my iCloud backup. Is there any way to access that iCloud file? I would be happy to either copy the backup data onto my iPad, or even just to get it in a text file. Been using this app to record workout results for 5 years and would hate to lose all that data.

[Re-Titled by Moderator]