If the Master Password is set on one device in a sync, it is likely set on all of them. No harm in trying, however.

https://support.mozilla.org/kb/Forgot+my+master+password Resetting your master password will remove all of your saved usernames and passwords. This is a security feature.

In the event that the passwords information is lost, you should record all information in a separate text file somewhere else on your hard drive, or written down. You can easily copy and paste if you need to do so. If you are concerned about someone else looking at that file, you can compress it using a password.

Password:Recovery:Restore

http://www.nirsoft.net/utils/passwordfox.html PasswordFox v1.58 - Extract the usernames/passwords stored in Firefox Copyright (c) 2008 - 2017 Nir Sofer

Note: Some anti-virus show false positive. ++++++++++++++++++++++++++++++++++ Easily export your passwords from Firefox. https://github.com/kspearrin/ff-password-exporter

Export your passwords from Firefox in a portable CSV or JSON format. It works on Windows, macOS, and Linux. +++++++++++++++++++++++++++++++++++ 3 Tools to Decrypt and Recover Passwords Saved in Firefox • Raymond.CC https://www.raymond.cc/blog/how-to-find-hidden-passwords-in-firefox/

TheNOLArtist said

If we cannot remember our Firefox master password on one device, but have no master password on another device for Firefox, would we lose all of our Firefox passwords on all devices?

The first answer made an assumption that Sync was involved ...

No. One device using the Master Password feature isn't going to touch the Logins on any other devices. Each device operates independently of all other devices, unless you have all 3 running Sync.

As far as Sync goes, if you are even using Sync, you can't synchronize Logins data on three devices unless they are all using the Master Password feature. Or they all aren't using a Master Password.

The Master Password feature will only Sync "like devices" as far as Logins data is concerned. All other data classes, as set in Options /Preferences per device will Sync, though. IOW, Bookmarks, Synced Tabs, History,, etc will, get synchronized regardless of the Master Password feature being used, or not.