We need to know more.
If you have the Control System Toolbox (or the System Identification Toolbox, or both) licensed and installed, both of those should work.
Example —
h = tf([50 0],[1 24 180 400])
h =
50 s
--------------------------
s^3 + 24 s^2 + 180 s + 400
Continuous-time transfer function.
H = tf([1 0.1 7.5],[1 0.12 9 0 0])
H =
s^2 + 0.1 s + 7.5
----------------------
s^4 + 0.12 s^3 + 9 s^2
Continuous-time transfer function.
More details would be appropriate.
Use the ver function to see if you have either or both of those functions. There are also versions in the Model Predictive Control Toolbox, DSP System Toolbox and the RF Toolbox. (I have none of those, however they would not be compatible with your posted code, from their descirptions in the online documentation. They require different arguments.)
EDIT — Corrected typographical errors.
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