Hi,
If you are looking for a three stage passive, then you can do this another way if your input and output impedance allows.
We start with an RC section of the right values, then add to that the second section where the cap value is divided by 10 and the resistor value is multipled by 10, then for the third section we do that again dividing the second stage cap value by 10 and multiplying the second stage resistor by 10. The output has a response that is very close to three stages of RC filtering where each stage has the same R and C values but the stages are isolated with a op amp with a gain of 1. The nice thing is, we dont need op amps for this design. The drawback is that the impedance of the input is relatively low and the output impedance higher so the application has to be ok with this.
For example, if we started with a 1k resistor and 0.1uf cap, the second stage would have a 10k resistor and 0.01uf cap, and the third stage would have a 100k resistor and 0.001uf cap.
Note that each stage is tuned to the same frequency, but the impedance grows so that the current stage does not load the previous stage.