Taifun
6
that directory is on the internal (emulated) sdcard, this is not a USB stick
Google changed how files can be accessed (details see here Some basics on Android storage system)
in your case you like to access non media files, which are not owned by your app
for this case you will need SAF
https://community.appinventor.mit.edu/t/panacea-is-saf-the-answer-to-android-file-restrictions/143403
in case you do not like to publish on Google Play you also can ask for manage external storage permission and use the current logic
also usually directory names are case sensitive… the correct directory name is /Documents
Taifun