If you want to use points to upgrade from economy to business, you would need to fly on Qantas aircraft. QFF can’t use their points to upgrade on partner airlines, regardless of if the ticket is marketed by Qantas with a QF flight number.
This means you really only have one option; using Qantas into London on the long-haul, and then connecting with partner airline BA to Milan in economy. One thing I’d keep in mind is that as a bronze flyer, you are very bottom of the list when it comes to upgrade priority so by no means is that upgrade likely. You’d be outranked by Silver, Gold and Platinum, as well as holders of paid Qantas club membership, frequent flyers with an earlier join date than yourself, and those travelling on more expensive economy booking classes or seeking to upgrade from Premium to business.
If you’re hoping to make the most of your loyalty, perhaps consider purchasing a paid premium economy seat and then requesting the upgrade to business with points. This will have the benefits of a) even if you don’t get the upgrade, you’ve not just paid a premium price for an economy seat - you have some added comfort, space, privacy and service b) your upgrade priority goes up a tad and c) you’ll gain more status credits, so you might go silver or higher and this will make upgrading easier in the future for you.
Hope that helps!