If you closely observe the below two images:
First Image: Model
Second image: Parameter Estmation Window
You can see the in the Model, there is an input (voltage) and an output (speed). Since this was defined in model, in the second image it is reflected as PE/DC Motor1(Speed) as Output and PE/voltage1 (voltage). In your model it appears that you do not have any input or output ports so it is not detected in Parameter Estimation.
Hope it helps.