I highly doubt any tool exist that will give you that information, at least not consistantly.
Other than password cracking tools that will actually crack the passwords of course.
The whole point of passwords and encryption is to scramble the password and not give information that would help an attacker.
If you’re using old stuff like LM Hash then you may get some information, depending on the hash values.
LM Hash is really weak, so if you’re using that you have bigger problems than password lengths.
It’s pre NT4 SP4 stuff.
If you want to make sure that all users have 15 or more characters in their password, you could set the domain password policy to 15 characters and then you would force a password reset.
E.g. setting the password expiry to a suitable short time frame and then reset it to what it was set later on, once everyone has changed their password.
Depending on the size of the company this may need to be done in a more staggered fashion and comms going out etc.
The only other option would be to start cracking passwords and that is a whole other can of worms.
If going this route, start looking at courses for Ethical Hacking so that you know what you’re getting yourself into.
E.g. get permission in writing etc.