With bikes, few things are outright impossible.
But something being possible doesn't mean it's sensible.
And upgrading a Next Power Climber is one of those.
Reason being that bike parts are a lot more expensive when bought piece by piece as opposed to when assembled as a bicycle.
By the time you've finished, you'll have spent MORE on the upgrades than what a new bike would have cost you.
And you're still left with a heavy frame with poor suspension design.
Best I can tell, the SLX Group rear hub uses a 142 mm thru-axle design, which won't fit in your frame.
Don't know if there are adapters available to turn it into a 135 mm Quick-release axle, which would be more likely - but not guaranteed - to fit your frame.
If you insist on throwing money away, it'd make more sense to buy something that'd fit straight off, as opposed to something that'd ALSO need to be modified before use.
Also neither fork or frame on your bike appears to have the required disc brake mounts.
For the rear, there are adapters available that - while ugly - actually work just fine.
Haven't seen a fork disc brake adapter I'd be willing to trust yet, even though there are some.
But I guess you're dreaming about replacing the fork anyhow.
So, get a jar.
Write "New bike " on it.
And every time you get the upgrade urge, go to the jar.
Stuff money into it until the urge passes or your wallet is empty.
Might not feel as fun, but trust me, the Power Climber is NOT good upgrade material.