My songs are missing from folders/library

Please ensure you have all your folders with music actually checked in Poweramp settings => Library => Music Folders.

Poweramp v3: Library / Ignore Short Tracks option skips short/unknown duration tracks, you may want to adjust that.

Your original Android Library is not changed, nor any files deleted by changing this option.

Poweramp library is a separate, completely independent library. When you installed Poweramp, it got filled with the files scanned
from your sd card/other flash memory, as specified in Music Folders. By default these are first available storage and /music, /mp3 on other storages.