So there's a couple of things to unpack here. Perhaps most of all, know your audience - 'where can I go instead of here to find the proper historians' is a slightly strange thing to ask the generally very real historians who, by definition, are here.

More conceptually, the way that historians go about their work does not lend itself to the kind of thing you're after. No one, to my knowledge, spends their time polling swathes of historians in order to tabulate their responses. While this state of affairs is partly because no one cares about historians' opinions enough to fund this kind of work, the main reason is because the kind of questions its possible to 'poll' like this are actually questions professional historians don't really focus on in their work. Historical research is focused on explanations, and a question like 'what was the turning point of the Second World War' (or, for example, 'who was the best president') does not actually help us explain or understand the past any better, and will always eventually boil down to subjective opinion. While historians may well hold such subjective opinions, they are unlikely to make them the focus of their work - you are unlikely to find a historian writing a book in order to claim that Midway, for instance, was the turning point of the war. They might write a book explaining how and why the battle was important, and its impact on the war, but it would be highly unusual for them to frame it as 'this is why Midway was the turning point, not Stalingrad or anything else. 'If anything, you're more likely to find historians explicitly arguing against there being any one turning point - that various broader structural factors (whether economical, political, strategic, diplomatic and so on) are far more important in explaining the outcome than any given battle or event.

So, with those caveats in mind, the gist of your question - how does one go about surveying historians' opinions on a particular question? - can be summed up in one word: historiography. This is one of the key skills that gets taught in university-level history courses: the ability to assess and analyse a field holistically, and use this to contextualise your own work. This is a vital skill when it comes to writing a history essay that actually makes sense - if you've been asked, say, 'what caused the First World War?' by your teacher, how on earth can you actually address such a huge question within the scope of a couple of thousand words, when it takes historians entire books? The answer is by building on those books rather than replicating them - identifying where there is currently still disagreement among historians, and focusing your answer on contributing to this ongoing discussion. Your answer then becomes less about summarising every possible thing that's relevant, and a more focused, in-depth discussion of particular points.

Historiography is hard, not least because it's not always an intuitive concept to everyone, but also because it means treating individual texts that you read less as self-contained units of historical knowledge, and more as pieces of a puzzle that add up to a 'field', requiring you to situate yourself as a more critical, detached observer - precisely the kind of skill we want people with history degrees to have. This in turn takes work - you can never just read 'one' text, but rather have to read multiple texts on the same question, spotting differences in approach and argument, and working out how they relate to one another. There are some shortcuts - most historians will situate their work within the field for you in the introduction, though, you can't always trust their choice of framing or their characterisation of other scholarship. Depending on the field, you might also find books or articles that aim to summarise the state of the historiography in a particular field. Academic book reviews can also be really useful in picking up what does or doesn't make any given book controversial. But, in the end, you aren't going to find out what a bunch of proper historians think about something unless you're willing to sit down and read what they wrote.