Great job with the geometry! One more edit to the horizontal frame bodies, draw a line across them at the center to create an edge to use in the Fixed Joints. If you want to do a 3x4 along the X axis, you copy everything except the three vertical frame bodies on the -X side, otherwise you will get double bodies in the center. You will also have to draw lines and extrude into sheets for the top part of the frame, which I left out of the single column version. Doing 3x4 will increase the number of Fixed Joints you have to make in the next step.
Use a Static Structural model to import that geometry. Assign the correct material (TPU) and thickness values to each sheet. Make all the Fixed Joints to tie the groups of edges together. It doesn't matter which edges are on the Mobile side and which edges are on the Reference side. The Fixed joints will have a Behavior of Rigid.
Create a Fixed Boundary condition on the bottom and a Displacement Boundary Condition on the top to push down the top by 30 mm and obtain the F vs D curve. You could have Standard Earth Gravity turned on too. After it has solved, determine the mass that must be added to the top to create the deflection needed to reach the flat part of the F vs D curve. Add that as a point mass to a single column or a distributed mass for a 3x4 array to the bodies along the top.
Drag and drop a Static Structural onto the Model cell, and in this, use just the Fixed Support on the bottom and Standard Earth Gravity to check that the model converges at the correct displacement.
Drag out a Transient Structural and drop that on the Model cell of the Static Structural. Use just the Fixed Support on the bottom and Standard Earth Gravity in step 1 and let the mass bounce up and down to get the frequency of vibration. Let me know what that is if you want me to create the 5 mm sine wave.
Finally, drag out a Transient Structural and drop that on the model cell of the Static Structural and do the three step analysis.
I will be available to help you all day Saturday and all day Sunday. Think about your professor reading this discussion. I expect he would have high confidence that you have the skills he needs when he sees you built the whole model and worked through the debugging phase without starting with the answer in hand.