I suggest you the great Software to recover Missing 7z file password without damaging saved data by the use of Atom TechSoft 7z Password Recovery Cracker in sometimes by following these steps:-
Download and install this tool in your system.
Browse the file which has to be open.
Select the recovery process from given three- mask attack, brute force attack and dictionary atack.
Click to proceed button and wait for sometimes.
Read More :- http://www.atomtechsoft.com/7z-password-recovery.html