how would I enter f(x) = 31.5 + 1.1 log(x + 1) in excel in order to graph it?

This is easier. y = 31.5 + 1.1 log(x + 1) - Wolfram|Alpha

Problem though Is LOG() LOG base 10 or the natural log (base e).

Enter the values 0 - 10 in cells A1 to A10. Then, type the formula

=31.5+1.1*LOG(A1+1) in cell B1 and drag it down to cell B10.

Now, click on Insert, Graph, and follow the instructions. You will get a graph of said function.