Create Parabool formule for profit calculation

I need help to calculate my profit for a certain price range.

I have three values available

Price range
Profit (factor)

For example, I fill the following start and end range:
start price range = 1
end price range = 1000

Profit for start range 1 = factor 3,04
Profit for end range 1000 = factor 1,0350

How to calculate the profit vs the range for example for price range 255?

Who can me apply the formule to calculate it?