Translation:I would like to buy fruit at the supermarket.
I'm pretty sure in this sentence 在 is just the preposition "at". If 在 were beong used in the ongoing action "-ing" sense it would be directly before the action verb. I don't think 想 ever means "like". 喜欢 means "like". In this case 想 means "want" or "would like". "Would like" is just a polite way of saying "want" in English.
That's because the "wanting" (想) refers to the whole situation of "在超市买水果“. Looking at it another way, "在超市“ must come directly before "买" because that location decribes the buying (买) not the wanting (想). If you said 我在超市想买水果 that would mean that while you are in the supernarket, you are suddenly overcome by a desire to buy fruit, which you didn't feel before you got to the supermarket, and stop feeling once you leave. It's somewhat nonsensical. Also, it sounds weird. If that were rrally the sentiment you were tryibg to convey, the English would be something like "When I am in the supermarket, I suddenly want to buy fruit."