我去过 <place> 。 [ wo3 qu4 guo5 <place> .] I have been to <place> 你去过 <place> 吗？ [ ni3 qu4 guo5 <place> ma5? ] Have you been to <place> ? 去过 [ qu4 guo5 ] is asked if the speaker is not at that place. If the speaker is at that place, they will use 来过 [ lai2 guo5 ] instead.

你去过中国的哪个地方？

你一直在中国哪儿？

你去過中國的哪些地方?

May I just say simply '... Ni qu guo zhongguo shenme difang? 你去过中国什么地方？ or do I need '...zai zhongguo (de shihou) qu guo shenme difang ...在中国的时候，去过什么地方？