How to copy pdf into asd and get list from asd

i want to store pdf files from device into the app (asd), and get list of files from asd, i tried this my self but not working, pls guide me iam a beginner

des should be path of destination file, not folder.

i dont understand, it will be mean copying file to file ? idont get it.
i try to gather my pdf in 1 folder/storage

i do understand now, thank you !

Hi, can you post an image of your blocks after correcting the problem please? Thank you