Yes, 8.546 = 8546/1000.
Remember that a rational number is the ratio between two integers. So any integer, like 8, is also a rational number because it's the ratio between the two integers 8 and 1:
8 = 8/1
So we have
8.546 = 8 + 0.546
= 8/1 + 546/1000
= 8000/1000 + 546/1000
= 8546/1000