what is the password External Hard Disk APFS After restoring from Macintosh HD

I don't know what happens to my system last time

I thought after updating system it was an accident with bug

my macbook pro don't want to open anymore, it remains black screen with white apple icon,

so I opened with internet mode "command + alt + R" to reinstall the system

but I have my files in the hard disk macintosh HD,

I did the method of restore macintosh HD to external hard disk,

So Macintosh HD has totally transferred to external hard disk with type APFS

external hard disk changed its name to Macintosh HD as internal exactly

after all that I did reinstall my system with success

but the problem is external hard disk named Macintosh HD with APFS type

he asks me the password, I put my all password but he does not accept any one

also the password of old my session before reinstalling

I want to know what is this password.
Please Help me