我们需要一个翻译，如果到时莉莉在的话，我们希望让她来翻译 怎么翻成英文

interpreter指口译，translator偏重书面翻译
hope后必须加从句，不可以说 hope sb to do，某人不要误导人家孩子
we need a interpretor. we hope that lily could come if she is here then.

we need a translator.If lily is there by then,we hope she could translate for us.
楼上的，虚拟语气，应该用could

I need an interpreter.I'd like Lily to do it if she is there.

We need a interpreter.If Lily is there then,we hope her to be one.

we need a translater,if lily is here,we hope let her to translate !