I ride Saracen cross 1. Now i want to update the hubs but i don't know which one will be best. I have two options either buy koozer or novatec. I want expert opinion which one will be best for me.
Also can i use those hubs in Saracen cross 1 2014 edition? i don't have idea about diameters.
Also can i use disk brake hubs in v brake?

You can use just about any hub you want subject to the following points of fit.

1- must be drilled for the same number of spokes as your rim.
2- overall axle width (OLD) and type (10mm standard, or thru axle type) must match your frame,
3- freehub body must be compatible with the brand and number of sprockets of your gear system
4- a disc compatible is obviously necessary for disc brakes. however it's optional if you don't have disc brakes, as long as other considerations are met.

Everything else is about personal preference and budget. Some brands and models are more durable, others lighter, some neither.

Thanks for the info.
Hoiw can i find the number of sprockets of my gear system? and which one will be better between koozer and novatec??

If you replace your hubs you'll have to replace spokes and nipples and might as well replace the rims. At this point you would be better to just buy new wheels.

You can use disk brake hubs on a v brake bike but you can't switch to disk brakes even with an adapter, fork might not handle torque. The rim would still have to have a braking surface.

There’s an adapter out there that lets you mount a disc brake caliper to a v-brake fork ? I always thought you just had to replace the fork with a caliper mount type fork.

for the long run get wheels with Shimano hubs, long term you can always get spare parts,
a disc hub without mounting the disc will be fine.

There are adapters that fit to the drop out and have arm that connects to the very brake standoff. RJ The Bike Guy did a conversion on youtube. At least for the rear. You might get it to work on the front but a replacement fork would be better.