Hi Yunus,
In the case of an asynchronous motor, the dynamics are quite complex with multiple inputs and multiple outputs. Therefore, a state-space model is more suitable to capture the complete dynamics of the motor. There is no direct block available for asynchronous motor using transfer function.
But if you have to use the transfer function for simulating the same, if you already have the "state-space" model, you can use the MATLAB "ss2tf" function. This function takes a state-space model as input and returns an equivalent transfer function. However, please the resulting transfer function might not necessarily be simpler than the state-space model. It’s just a different representation.
You can read more about "ss2tf" here:
Hope this helps!
