First in my understanding you dont need to convert it too long
Just make the 10th power same like exponent of 10's.
if u are comparing two number try to make their 10 ^x factor same
9.98*10^6 kilogram 998*10^4
7.3*10^7 kilogram 73*10^6 this is greater
73*10^6-998*10^4
10^4(7300-998)
10^4( 6302)
6302*10^4 or u can write 6.302*10^7 more