Hi Kelly,
Could you please add a bit more context to your question? Is that correct, your page type's multichoice field stores a bunch of keys (or IDs) and in the repeater you'd like to select connected objects by these keys?
If so, if you expand Advanced configuration of the multichoice control there will be a separator field, which is pipe "|" by default. If you change it to be comma "," then you'll be able to use this value in Where condition of your query datasource.