Confidence intervals and Bayesian econometrics do not square well. Bayesian look at credible sets. What exactly do you mean? The second number in the specified prior is the standard deviation of the prior, which gives you an indiciation of the prior precision.

what is the credibel set (interval ) that this particular prior defines ?
Can I calculate it or is dynare calculating the posterior credible set and that should also be the prior credible set (is it the same ?)

in one of the papers it says :
I am setting this particular prior so that the 95 % credible set is this m;n] (some values) …

At github.com/JohannesPfeifer/prior_from_quantiles you can find codes to compute quantiles for various distributions. See Koop’s textbook Bayesian Econometrics for a definition of a credible set.