The purpose of the party is to give a treat to my family members, as my immigration into New Zealand is approved.

immigration 是名词，由前缀 im-（表示"进入"）和词根 migrate（迁移）加上名词后缀 -ion 组成。字面意思是"迁入"，特指"永久移居到另一个国家"。 immigration into New Zealand 指"移民新西兰"，即获得新西兰永久居留权的过程。