Use the EE or EXP key on that calculator. You will have one or the other, but not both. This key has been designed to enter numbers in scientific notation. If you are using the 10^x key, then you should stop because that key was not designed for scientific notation. 

To enter 3.0 x 10⁸, all you have to type in is  3.0 EE or EXP 8. 

That’s it. The EE or EXP takes the place of the x10 part. You should also be able to make the exponent negative as well by using the +/- or (-) key, and again you will have one or the other but not both. 

To enter the final calculation for Chemistry, Example 3.2 (p. 103), type in the following:

3.0 EE or EXP 8 divide 4.05 EE or EXP (-) or +/- 7 = 

Your display will probably look like this: 7.407407407 14  

The 14 will be set apart from the other numbers. This 14 is your exponent on the 10.

You will need to round the decimal part to the correct number of sig figs:  7.4 x 10¹⁴