While York were securing their first win in six league games at Rochdale last week, Plymouth slipped to a third straight league defeat at home to Chesterfield and have failed to win any of their last nine games in all competitions.
But Mills said: "We were in a similar position last week and got our first win for a while. I think it took us eight games to do so, but we knew a result was coming.
"So we know in this league how close it is. A win for them could be just round the corner. We know how unlucky we've been in games, drawing some we should probably have won.
"It's a long trip to Plymouth and we know how hard they're going to make it for us. We took our chances last week at Rochdale and got what we deserved, but we'll have to work just as hard against Plymouth."
The Minstermen's 3-2 victory at Rochdale was their first league win since a 1-0 success at Accrington on October 23, but while Mills' side have slipped to 14th place in the table, they are still only four points adrift of the top seven.