The find peaks tool utility is only available with the Simscape and the DSP System Toolbox : https://www.mathworks.com/help/simulink/ug/simulation-data-display-and-capture-using-scopes.html#buw7l4r-5
As a workaround you could probably use the MATLAB function for finding peaks which is available in the Signal Processing Toolbox : https://uk.mathworks.com/help/signal/ref/findpeaks.html
If you are not able to use any of those toolbox , one thing you could try is to use a function from File Exchange and use it in your model to find the peaks you was looking for : https://uk.mathworks.com/matlabcentral/fileexchange?q=find+peak
