updating the whole contact list

Hi, I have a contactList with already 800+names. My clients is asking me now to link this list with their database by inserting an ID field in the wix contactList. So basically I need to take every contact I have in my contactList and match it to a name in a cvs file they will give me, take the corresponding ID for that name and update that contact in the contactList… Any clue on how I can do that? It’s a ngo and I really would like to help them. Thanks