What type of power converter/adapter/transformer will I need to use a U.S. purchased blender in Korea?

Here are the details of the blender:

120V, 60Hz, 350W

I know it would probably be easiest to just purchase a new one, however, I need to bring this exact one.

You are getting good advice from everyone. If you are in Seoul bring a Korean friend with you to Yongsan. You can buy a step down transformer here for 30 to 50 dollars. Make sure you get one with grounding.

First see if your appliance is dual voltage; if the rating says 110-240, then you're OK and won't need a converter.

If it isn't dual voltage, check the wattage rating on the blender. Use a converter that is rated at least 25% higher than your wattage rating.

2 things,
Is your apartment dual voltage?
If not....you can pick up a cheap "Step-Up transformer" at any electrical store...easy to find in electronics mart or at the US Base re-sale store...($10/20)....probably cheapest of all is to buy a used 220v blender ($10/20)

You need a step down transformer to step voltage from 220 to 110 . They are generally available in some big stores such as hardware , maybe building supply and possibly in appliance stores

If the blender is the only thing you need to plug in just take the numbers to the store and they will show you the right one. Pay attention to the number of prongs the transformer will accept.
If the blender is not the only appliance you plan to use, I would buy a stronger transformer and run a power strip from it for every thing.
Also, depending on your area the landlord may be obligated to provide you with one. In my town it is either law or homeowner association strong arm (I never figured out which) that the landlords have to provide for the power conversion.
Last, someone mentioned about dual voltage. This can either be by way of a switch or by way of a big bulky plug that is basically a transformer. If you have one of the big bulky plugs read it to see what power levels it can handle. Many are good from 110-240v. Then all you need is the 500 won plug adapter.

The only thing I'll add to the above excellent answers is that most of Europe uses the same type of power so any transformers from there (bought from a friend or from previous residency or whatever) will work too.