Hi Aashish,
As per my understanding I presume you are unable to connect and read data from 3 sensors simultaneously in Simulink. For this you can put 3 Digital Input block as shown.
You can later add a MUX block from Library Browser if you intend to combine these digital output data.
You can also add a MATLAB Function block. By using a Function block, you can perform operations such as filtering, scaling, thresholding, or any other signal processing tasks on the digital input signal before it is sent to the output block.
Refer to the documentation below from MathWorks about Simulink Support Package for Arduino Hardware
I hope this resolves the query you had!