If this is a stem... ... what's this? I'm asking because I need to buy a taller one so I don't have to bend over as far. It's not convenient to buy a new bike, and I already have an adjustable stem which just doesn't quite get me there.
Once you unbolt the stem, the forks can just drop out if you're not careful. Replacing the forks may not be economical to replace, and if so, I'd replace the whole bike. Good luck. :)
Actually, having said that, the steerer is already ridiculously high; I'd recommend time to replace the whole frameset, as making it too high can be dangerous, if not deadly depending on when and how it breaks. If you're going downhill and the steerer snaps from being too high and too much force going through it, it can shatter or snap, and if you fall on that, it will seriously injure you, if not killing you. Replace the frameset rather than just the forks. The whole bike looks too small for you.
What you are referring to is not really a discrete component that can be swapped out.
The fork steerer tube runs through the frame 'headtube' and headset bearings. The stem clamps to the steerer tube. Between the stem and frame are a stack of spacers.
The maximum height of the stem is therefore constrained by the length of steerer tube.
Forks come with a long steerer tube to accommodate different length frame head tubes. When fitted to a bike the steerer tube is cut to length, usually with a few inches protruding from the frame, so the stem can have 1-2 inches of spacers underneath it. The length of tube left protruding depends on the type of bike.
I would guess from your picture that your steerer tube has not been cut down at all, and the stem is obviously at the top of the steerer tube. Some possible solutions:
There are steerer tube extenders available but I'm a little reluctant to recommend you fit one as you steerer is already so long. Others here may indicate that is is OK to do so. You may also want to consult with your local bike store.
You may be able to find a replacement stem that gives you more rise.
As @mikes suggests in comment to another answer, replacing the bars with a set that sweep upwards from the stem clamp to raise the hand grips up may be a good solution.