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 8.45:
Use your calculator to find InvLn(8.45*2.303) = InvLn(19.460). Then AntiLog(8.45) = InvLn(19.460) = 2.827x108 (close to answer of 2.818x108.)
To get better agreement, use the more precise value of the conversion factor: 2.30258