I think it means like "I/you did this for you/me so this..." but the phrase is not complete so it's hard to understand.
Example.
네가 도와해주나깐 이걸 좀 받아. = "You helped me, so please take(recieve) this."
2015年1月31日
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해주니깐 = 해주니까는 --> 해주니까+는
이걸 = 이것을
지금 바쁘니까 나중에 전화할게 --> I am busy now, so I'll call later.
To explain your phrase 해주니깐 이걸, why don't you give some situation or context?