V-brake to disc brake
This can get expensive, so check the costs before committing.

You require a disk brake caliper and lever, which might be a sealed hydraulic unit or a cable-operated one.

The caliper needs to operate on a disk rotor, and the rotor needs to fasten to the disk compatible wheel hub.

It is probably cheaper to buy a new complete disk-compatible wheel rather than rebuild your current rim onto a new disk compatible hub.

Also check the mount on the new fork - if it's for a through-axle then your new wheel needs a through-axle compatible hub. QRs seem to be vanishing.

Depending on your grip condition, you may need to replace them too.  May need to cut the old grip off to swap the brake lever.

Your tyre and tube should transfer over okay, assuming they aren't worn.