How do I do this problem with exponential numbers and whatnot?

It’s been a few years since I’ve had math and I’m rusty. Now, I’m in Chem and banging my head on the desk because I can’t remember how to do this. This is not homework, these are just practice problems, but I need some help, please!

I have the problems and solutions, which are basically getting a scientific notation number into some other form, which varies depending on the problem at hand, but I’m not so worried about that because I fully understand canceling. Basically, what I want to know is how to handle the ^n numbers.

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The solution is written out as:

6.54×10^9 fs x [(1×10^-15 s)/1 fs] x [1 μs/1×10^-6 s] = 6.54 μs

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My question is, in a problem like this, how do you handle the scientific notation numbers? I’ve completely forgotten.. I remember you add sometimes and subtract others? I wrote the thing out and tried to cancel and work it out for myself, but I don’t get it. I do understand the principle of the rest of it.

Your help would be most appreciated. :)