He would have most likely gone by Conrad here and Johnson but there are always exceptions. Searching the 1910 census by place of birth is not a good idea as about only half the names show place of birth in the index.
There is a Conrad Johnson in the MN Death Index listing his date of birth as February 6, 1882. There are two Conrad Johnsons in Minneapolis in the 1920 and 1930 census but they are Swedish and the immigration dates don't match:
I think he was there for a short time only, but i don't have the details. Because he went back to Norway and started a family here. One son of his was born in 1922, so....
And I am kind of curious about the chances of any children in America. That would have been really fun