Per sig, since have a Mac, can try looking under '~/Library/Mobile Documents' to see if a folder there that corresponds to the app.
Might be able to see the folder in the Files app on the phone: some apps will create their sandbox for data and make it visible. For example, a snippet from my phone:
View attachment 2644868
Mac programs like iMazing can make navigable backups of iDevices where one can maybe export whatever sandboxes the apps make.
But in all these (most) cases, files/data might be in a proprietary format, so will need to decode that.