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Tell us exactly the parts you need and maybe we can help. I had a similar problem a while back with a cheap Chinese bike that had a mix of SRAM, Shimano, and off-brand parts, it can take time to figure out what you need because there is no official list of components on any webpage.
I'm pretty sure you have mechanical disk brakes, probably very low end SRAM Avid's, which I've had previously on a couple of other bikes and I could not stand them, heavy bike or not. Do yourself a huge favor and replace them with hydraulic brakes. You don't even need to go to a bike shop to have them installed if they are pre-bled.