To convert a natural antilog to a base=10 antilog, multiply by the conversion factor 2.303 before taking the natural antilog..
For example, to calculate the base-10 antilog of -3: Use your calculator to find InvLn(-3*2.303) = InvLn(-6.909). Then AntiLog(-3) = InvLn(-6.909) = 9.99x10-4 (very close to exact answer of 0.001)