Extrapolating Missing Data

What specifically do you need help with?

If this is a "I have no idea where to begin" kind of thing, here's how I would analyze the data:
1) put the data in a spreadsheet -- level in one column and exp in a second column
2) Plot the data on a scatter plot with one column along the x axis and one column on the y axis.
3) Look at the chart and see if anything obvious becomes apparent.
3a) Switch X and or Y axes between linear an logarithmic to see if this causes the data to form a straight line
3b) compare the shape of the curve with the usual families of curves (quadratic, exponential, logarithmic, square root, etc.) that I recall from algebra/calculus. If you need a refresher on these: http://mathfortress.com/Precalculus/...0Functions.pdf
4) Hopefully at the end of step 3, I have some idea of what the regression equation should look like, so I set up the regression. Exactly how to set up this regression depends on my conclusions at the end of step 3.

With the problem broken down in steps, where do you get stuck?

I took the liberty of doing what MrShorty suggested and the result is that a third-degree polynomial is a perfect fit for your existing data. Attached is a file that plots your points on a scatter graph. I tried various fits and the one shown has an R² of 1, which is perfect (0 is no fit). The equation is shown on the chart. You can use that equation, where x is the Level, to give you the number of points for that level (y).

The short answer to your question is Excel does not do interpolation* automatically by dragging values but it gives you enough tools to do it yourself.

*Interpolation is filling in gaps within the known range of data, which is what we have here; extrapolation is extending your data outside the range for which actual data exists.