Where does the に particle go in a sentence when we want to indicate purpose?
Can you provide some of the context that led to you asking the question? There are many ways to indicate purpose, and some of those expressions include the particle に.
For instance, [verb stem]に行く (to go to for the purpose of doing some task)
話しに行く (to go to talk)
見に行く (to go to see)
探しに行く (to go to look for)
But that’s not the only possible way to express that you are doing something for a purpose, so I don’t know if it addresses your question.
Well I came across two sentences: 映画を見に行った。& 昼ご飯を食べにうちに帰った。
The website said they were used to indicate purpose but gave no explanation whatsoever.
Okay, so it’s that grammar point. Yeah, it’s just a way of saying that you are going somewhere to do a specific thing. As you noticed in the second sentence, other things can come between the に after the verb stem and the verb of motion if necessary. It doesn’t have to be 行く, it could be others, as you also see.