Add MFA

[Emjos]

Hello Everyone.
I'm hoping someone can assist me with a question. I'm looking to add MFA (Multi-Factor Authentication) to my OpenVPN server. I want to require users to provide their username, password, and an MFA code in order to connect. I've attempted to set it up on my own, but I'm having trouble locating some of the PAM (Pluggable Authentication Module) files. Any guidance or assistance would be greatly appreciated.

Thank you!