"Simulating" a mass/spring/damper with Simscape is simple, refer to documentation here:
https://www.mathworks.com/help/physmod/simscape/ug/creating-and-simulating-a-simple-model.html
I believe you want to "animate" the mass/spring/damper system using SimMechancis (now called Simscape Multibody) which not going to be as easy. The solid block in SimMechanics creates rigid body which means the spring will not compress or extend in the animation. You could create several discrete elements of the spring and then link them together. It would be similar to creating a flexible beam as in this example:
https://www.mathworks.com/matlabcentral/fileexchange/47051-flexible-beam-in-simscape-multibody
