Zero

Jason:
The D&RGW did not provide any cars to the CB&Q for the fair.
The three cars ( there may well have been 5) that were used with #9 were all converted by the C&S from steel framed cars in 1939, when the #9 was shipped to Chicago for the World's Fair.
Following the 1939 World's Fair, the entire consist, which also included an RPO, Coach, and Business Car #911, was stored in Aurora, Illinois. It was later restored servicable at the CB&Q shops for the 1949 Chicago Railroad Exposition, stored again, and eventually "leased" to the ill-fated Black Hills line.
I recall that some steel framed observation gons were used at Heratige Square. These were the first of the ex-C&S equipment to find it's way home. If only three of five cars were returned, I have no idea where the other two went. Later, all remaining former C&S equipment in the Black Hills was brought back.
The D&RGW converted 4 High Side Gons for use at the 1949 Exposition. They were named "David Moffat", Brigham Young", John Evans", and Heber C. Kimball". Combine #212, and Business Car B-3 were also shipped to Chicago for the event, along with #268. The B-3 was decorated and lettered as the "General William Jackson Palmer". At least some of the converted gons were later used at Central City, and are now at Georgetown.
I don't know if this helps or not, but I am confident that none of the equipment displayed by the CB&Q in 1949 came from the D&RGW. They already had everything they needed.