Find the underlying normal distribution of a folded normal distribution

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This might be a very basic question, but I haven't found a clear answer anywhere, so I hope someone here can help.

How does one find the mean and standard deviation of a normal distribution that underlies a folded normal distribution?

In other words, if you have data that follows a folded normal distribution but want to "unfold" it, calculate the mean and stdev of the unfolded distribution, how do you go about it?

To go by an image (from Wikipedia). I have the green curve, but want the purple line:

Is it simply the mean and stdev from the folded normal equation, as described here?

Or is it this equation?

Cheers!