You did not specify which transfer function you want. Let's assume you want a transfer function from input voltage to output voltage.
1. Start a new Simulink model and add Capacitor, Inductor and Resistor blocks from Simscape, Foundation Library, Electrical, Electrical Elements:
2. Add Controlled Voltage Source block (from Electrical Sources sublibrary) for providing input voltage, Voltage Sensor (Electrical Sensors sublibrary) for measuring output voltage, also add Electrical Reference (ground) (Electrical Elements sublibrary) and Solver Configuration block (Utilities sublibrary in Simscape). Connect the blocks as shown in your image, and specify all the values as shown in the image.
3. Add Simulink-PS Converter and PS -Simulink Converter blocks (also from Utilities sublibrary) for converting Simulink signal to physical signal and back. Use Step block as an input to the model, and Scope as the output.
4. Now right click on the line coming from Step block, and select Linear Analysis Points - Input Perturbation. Right click on the line coming from PS-Simulink Converter block and select Linear Analysis Points - Output Measurement. Note that this requires a license of Simulink Control Design .
5. In the menu select Analysis - Control Design - Linear Analysis
6. In the Linear Analysis Tool click on Linearize:
This linearizes the model, plots the step response (or some other graph if you selected something else, Bode plot, for example) and adds a computed linear system to Linear Analysis Tool workspace:
8. Copy linsys1 to MATLAB workspace (drag and drop in Linear Analysis Tool).Now you can look at the formula and use the linear system for further analysis and design