These cards were issued in 2000 Cubs Quarterly Magazines, in 9-card panels. So there were 36 total cards that year, but each issue had a different sponsor and design. I have two of the issues I can dig out and get the 18 cards from, and might be able to do a full 36 card checklist with a little digging. The magazines they appeared in were:
April/May 2000, Vol 19 No. 1 (Don Baylor cover)
May/June 2000, Vol 19 No. 2 (Mark Grace cover)
July/August 2000, Vol 19 No. 3 (Kerry Wood cover)
August/September 2000 Vol 19 No 4 (Sammy Sosa cover)