This link is a PDF version of the catalog and the Finding Aid for the Minnesota Historical Society’s Dakota Conflict of 1862 Manuscripts Collection. The manuscripts are available in the Hubbs Room in the Library at the History Center in St. Paul on four reels of microfilm cataloged as M582.
The rolls of microfilm have been digitized by MHS and are also available on the web. Use the catalog linked above to find the location of manuscripts of interest, then go to the PDF of the corresponding roll of film to read: Roll 1; Roll 2; Roll 3; Roll 4.
However, the PDF files are huge and slow to load. For faster navigation, use the on-line version MHS supplied to archive.org and choose “Read Online” from the menu in the upper left: Roll 1; Roll 2; Roll 3; Roll 4.