Is the Encryption Key for Adoptable SD card included in manual backup done over MTP? I did a factory reset and then realized that I didn't decrypt my SD Card. I know that the data is probably lost, but I made a complete copy of the Internal Storage connecting the Samsung J5 mobile to a PC (drag and drop, i know this is not the good way). Now I can't find /data/misc/vold to locate the encryption key file like i read in other posts.
Is there a posibility to read this folders with a linux virtual machine installed in the PC and recover the encryption key file, or it has dissapear forever?

A use MTP for file transfer
Unfortunately, what you have so far considered as the complete copy of Internal Storage is not true. You only copied (I suppose using MTP - "transfer files" option) your files which you had created or downloaded in that storage since last factory reset. The app and system specific private files are never copied in this fashion. /data/misc/vold cannot be copied directly using MTP. A user needs root access to access that file (includes copying it).

In conclusion, you have hit a dead end on this part.