Passcode protected Notes iOS changed

Without my asking, the passcode I had set to unlock protected Noyes was changed to the iPhone pass word after a system update.

That is not what I want: family members may unlock my phone and iPad for convenience and safety, but my locked notes are for me. Worse: my MacBook pro now tells me to update MacOS in order to open those Notes. Using my MacBook’s passcode or the one I use on iOS doesn’t work. It’s an older model and won’t update any further.

Who can help me set a unique passcode that I can use to lock/unlock the same Note across all devices?