Ideally your lecturer would have covered a data structure to use in the course material. It would be rare that the exercises do not match up with the material the lecturer has covered.

Maybe if your course notes are incomplete, talk to other members of the course.

There are many approaches to linking data from two lists together. The most common approach is to take the shorter list and put its elements into a hash. Then, for each element in the longer list you take the key of the element and look that up in the hash.