Hi Colleen -- thanks for posting to History Hub!
The unpublished records of the U.S. Congress are held by the Center for Legislative Archives, a unit of the National Archives. You can connect with a legislative archivist by emailing firstname.lastname@example.org.
The best way to identify bills is through Congress.gov, the official website for U.S. federal legislative information. Congress.gov will have information on bill numbers, Congresses, and to which committee(s) each bill was referred -- and Congress.gov covers from 1973 to today.
You can then search the National Archives Catalog to see if there are records specific to your topic -- for example, it looks like there are 5 boxes from the Senate Committee on Labor and Human Resources in the 93rd Congress relating to the Domestic Volunteer Service Act of 1973. If you use the 'Advanced Search' in the Catalog, you can limit your search to Record Group 46 for records of the U.S. Senate or Record Group 233 for records of the U.S. House of Representatives.
Please note that due to the COVID-19 pandemic, our facility is currently closed. We do not have access to original, unpublished records in the stacks during this time. We're happy to work with you to access records when it's safe and possible to do so.