error in dimension for adder in negative feedback loop
B matrix has only one column. So single input. The figure indicates that gain block Kc tries to have 3 outputs which cannot fit into the input of the system. The gain in the gain block needs to be a scalar.
Edit
From the Matlab documentation website

place computes a gain matrix K such that the state feedback u = –Kx places the closed-loop poles at the locations p.

The place command is for state feedback. But since you have a C matrix with only one row from which you are feeding back, you need to use a technique which uses output feedback, not state feedback. This is why Kc turned out to be a 1x3 matrix instead of a scalar. For a SISO system with output feedback, the feedback gain should be a scalar value.