"I worked for that company for three years."
This is just me trying to make sense! Please correct me if I am wrong.
In English the topic is: "for that company" therefore starts with, そのかいしゃには つとめる means to work (for), so that's why "worked for three years" translates in Japanese as: 三年つとめました I think it wouldn't be wrong if you put 三年 in front of the line while placing the , with it --> 三年, その会社には勤めました。
Since work is a location in this line you'll have to use に as well together with は to add emphasis. It's why に is often referred to as the location or time marker.
I tried 三年はそのかいしゃにつとめました。Is there anything wrong with that? Or is it not explicit enough what the "three years" there belongs to?
I feel like that is wrong, because you're making the three years the subject and not the place. To translate what you wrote, it would be something Iike "As for three years, I've worked in that company." By specifying the company (as a place) as the subject, then saying you've worked for three years, you become more clearer in meaning. "As for in that company, I've worked for three years."
I have this question too. I keep putting:
Even Microsoft's IME doesn't provide the kanji when you type the 2nd one out like it does for the first one. If anyone could explain why it differs, I'd appreaciate it.