pressure tank

I have a cabin but no power, can I use gravity flow from 300 gallon holding tank 40 ft of elevation 250 ft distance from cabin to fill pressure tank to supply water to cabin What size line should I use?

For 300' I would use 1". 40 feet of elevation gets you about 17.6 psi, which is marginal, but it is what it is, for a cabin.

How do you get the water up to the tank?

If the pressure you can get with the gravity is enough, there's no reason to put a pressure tank in the house. Only if you want more pressure and pump it up higher would one help. The pressure tank won't add any pressure, they just store what you have. Their primary purpose is to prevent the pump from short cycling if you, say, run the water momentarily to brush your teeth. With a large supply on the hill, a tank in the house would add nothing without a pump except take up space.