Where can I find some primary sources about the Hinckley Fire or 1894?
See the Hinckley Fire Museum link below. It has some primary sources resources.
You can find some newspaper articles from the time at the Library of Congress' Chronicling America site.
You can find some images at the Minnesota Historical Society.
The Historical Society also has a translation of a booklet from the time about the fire. You'll have to ask your instructor if it counts as a primary source.
A thesis on this subject has some primary sources in the bibliograpy you may find useful. The title is "A Memory in Fire."
You might also find the Pine County Genealogical Society's webpage helpful.