The best way to do this is to make a backup of the app's Containers folder. You can access the Containers directory by opening Finder and pressing CMD + Shift + G keys all at once. This will open the file path navigation prompt. In the prompt, please type the following and then press enter: ~/Library/Containers
This will take you to the Containers folder on your hard drive. Within the folder, you should make a backup of the relevant app folder. For example, if you want to make a backup of your MiniNote Pro data, you should make a copy of the 'com.fiplab.notestabpro' folder within your Containers directory and save it to your backup drive.