From the $3 \times 3 \times 1$ supercell and the $\Gamma-M-K-\Gamma$ path, I assume that you are investigating the band structure of a two-dimensional material with a hexagonal structure. Therefore, maybe the simplest way that you can follow immediately is using the VASPKIT package.
Coincidently, the example tutorial is about monolayer MoS2: https://vaspkit.com/tutorials.html#band-unfolding
Hope it helps.
BandUP: Band Unfolding code for Plane-wave based calculations
This software can help you. From the developers site:
BandUP is a code that allows you to obtain a primitive cell representation of the band structure of systems simulated using supercells. The unfolding of the bands is performed as described in the following papers:
Paulo V. C. Medeiros, Sven Stafström and Jonas Björk, Phys. Rev. B 89, 041407(R) (2014)
Paulo V. C. Medeiros, Stepan S. Tsirkin, Sven Stafström and Jonas Björk, Phys. Rev. B 91, 041116(R) (2015)
Information about the code: http://www.ifm.liu.se/theomod/compphys/band-unfolding/
And source code ready to download: https://github.com/band-unfolding/bandup