There is a few ways to go about this. The way I think about it is to use the commutative and associative properties and set it up to read
(4x2)x(10²x10³)=? Using your Order of Operations (PEMDAS) from here on out, along with the rule about adding exponents with a common base...
(8)x(10^(2+3))=? Still not done, and we actually created an extra set of parenthesis. Lets remove them this round and clean it up some.
8x10^5=? It looks much better, and now you can easily expand your equation out. A rule of thumb about "10^__" is that you move the decimal place that many places over. + numbers the decimal moves right, negative... it moves left.
8x100,000=800,000. Hopefully this helps. Good luck!!