how to reassemble mountain bike rear wheel hub and bearings
While not necessary, it will probably be easier to understand what is happening if you lift the cassette off. The ring at the front of your photo (C) is the nut that holds the cassette on, so right now you should be able to lift the cogs off the freewheel. That will leave you with the splined body of the freewheel exposed and you'll have one less distraction.



The parts labelled are :

A: cone locknut (the last thing to go on)

B: seal, probably from the drive side

C: cassette nut/lockring that holds the cassette together and onto the freewheel

D: spacer/washer that goes between A and E

E: cone with seal attached

F: seal from the axle and cone labelled H

G: seal from the non-drive side

H: axle with cone attached.

I: there is no I

J: washer. I have no idea where this goes.

K: quick release axle.

Ignoring the bearings for a minute, the order things go back in from the non-drive side (underneath, in the photo) of the wheel is likely to be: Put the seal F back on H from the long side - it probably should not go all the way to the washer. Push H up into the wheel screw E down onto it then add D, screw A down and lock it off. Push G over the non-drive side cone assembly to seal that side. Push B into the drive side if it fits (I'm not sure it will, I haven't seen a seal like that or in there for a very long time). Put the cassette cogs back on, then add C to lock them in place.

Before doing this you will have cleaned the old grease off the cones in the hub (careful with solvents, you don't want to wash the grease out of the rest of the freewheel), then put in new grease and pushed new bearings into it (the grease holds the bearings in place while you reassemble).