First, the instructions to the enumerator as to what to put in Column 34, if the person indicated they lived on a farm, can be seen in paragraph 598 at:
http://usa.ipums.org/usa/voliii/inst1940.shtml

It is not clear to me, and I have an original enumerator handbook for both population and agriculture, is whether the "number" is a schedule number or a number that can be used for cross referencing. I doubt the latter as the enumerator would have to have a predetermined list of numbers to use.

In any case, I doubt that the individual farm schedules have been preserved, only summary information exists today. If the 1940 housing schedule was destroyed before microfilming, it is likely the other schedules other than the Population Schedule, met the same fate.