上个星期你和老王是在哪里见面的？

no um 上月 is not correct . BTW 老李 is Lao Li 老王 is Lao Wang. and 上個星期shàng gè xīng qi is last week you could say ? 上個星期你和老王是在哪里見面的?

I think you COULD use 是。。。的 form, but it is certainly not necessary - the you last week met lao wang place [是] was where [的] ??? 但我不一定。

月 is month, 星期 is week

I'd say "上個月你跟老李是在哪儿見面的？"