Formatting an Exponential Number

It will not happen through formatting. Off the top of my head, you will have to convert your number to a text string with the appropriate elements. A formula like: =CONCATENATE("-6.102","x","10-8") or =SUBSTITUTE(TEXT(value,"0.000E+0"),"E","x10"). Then, in order to superscript the exponent, you will need to copy and paste as values to get the text literal, then you can format the exponent part of the text string as superscript.

No. In order to get the exponent superscripted, you have to convert the result of the formula to a text literal/constant, which means that it cannot continue to be the result of a formula. When you want to do something like this, you have to decide if you want the exponent superscripted, or if you want the cell to be the result of a formula (or you can come up with VBA/Macro code associated with the calculate event that will take the text formula result and write the result into the cell as a text literal and apply the appropriate formatting to the exponent characters).