Troubles on changing the root password

[Vinicius Barros VIni]

Hello everybody!
When I first installed the MySQL 5.7.21 on my computer, I put a random password for the 'root', during the installing process. Then, some days later, I got some troubles using the software - I wasn't able to create different profiles with lower privileges.
I uninstalled the software and during the new installing process I didn't remember the old password. Then, it failed during the Apply Configuration process, specifically at "apply security settings" and I got the following message at the log tab:
"Authentication to host 'localhost' for user 'root' using method 'mysql_native_password' failed with message: Access denied for user 'root'@'localhost' (using password: NO)".
I tried to create a new password with a text file by cmd using the code below, but it also failed.
C:\> cd "C:\Program Files\MySQL\MySQL Server 5.7\bin"
C:\> mysqld --init-file=C:\\mysql-init.txt

I'm a simple user and any kind of help for this case will be well accepted.