You have a few options, but just a note: since you’re from QLD, your QLD ATAR may translate to something different in VIC ATAR, so your 75-80 estimate may =/= 75-80 ATAR in VIC.
1. Internal transfer: this means that you can try to get into another course e.g. Arts at UoM and attempt transfer into Science after a semester or two. This usually requires you to have a certain Uni grade and is generally the most successful option.
2. External transfer: this means you get into another course (anywhere else) and transfer into UoM after a semester or two. This usually requires you to have a certain Uni grade.
3. Bridging course: since you didn’t the Methods, you can try a bridging course - a short course that raced through Methods content. After successful completion, you will be considered to have completed the methods prerequisite for Science, but due to your estimated ATAR, might still be not quite competitive enough for entry into Science. You should ask the uni if this pathway would get you in if you’re interested in it, as your situation is a bit more complex with state ATAR conversion. This does have the benefit of being relatively quick though from what I hear.
4. Postgrad course or Honours: if you’re keen on UoM but can’t make it in for some reason and have a particular interest within science that you want to study e.g. engineering, then you could simply do your Bachelor of Science elsewhere and do Honours or postgrad studies at UoM. However, you will need to make the prerequisites of those with your BSci elsewhere.
Hope that helps!