What is the upward force that balances the weight of an object on a surface

Bouyant is the answer.

The support force / Normal reaction force

Explanation:

Refer to Newtons third law.

"The third law states that when a force acts on a body due to another body, then an equal and opposite force acts simultaneously on that body"

Since we have a downward force acting on your object, in this case gravity/weight, there is an equal and opposite force given off by the surface the object is on. This is called the support force or the normal reaction force