There are many methods available but in my opinion you need a Password Recovery Software.
PassFixer 7z file Password Recovery Software having quick methods which contain the lost Password with 2-3 Steps. They also gives 100% data security while recover the password of 7z file, User of any kind of Windows OS operate it, Its auto saved the recovered password on Clipboard, Mainly they have three advanced features- Brute Force Attack, Dictionary Attack and Mask Attack whose make easy to operating the software and quick result of recovery process. They also provide a Free Demo Trial in which the software shows you the first three characters of your password which gives the consumer assurance of the product and Service.
Read more:- Instinct method to recover the 7z file Password