I mean, how can I set the program to show me where is the value of 4,51 ; 4,52 ; 4,53 and so on...
I'd question weather it's a spectrogram that you need.
A spectrogram is more for visually analysing frequency changes over time.
It would be better for you to use a frequency analysis graph/spectrum analysis graph. I think it's labeled as 'Plot Spectrum' in Audacity.
Audacity is not the best for analysing in this way.