Mullins extended his stay with the Millers on Friday and after another solid game at the back against Plymouth on Saturday, he's looking for the side to push into the play-offs.
"League One is achievable, but we know it's going to be difficult," he said to the clubs official website.
"There's a lot of football to be played and it's a lot to ask but six points in the next two games would put us back in it. We genuinely believed March was going to be a big month for us and now we have just got three points, we have to get back up for Tuesday as we are playing a very good Torquay side.
"The club's going places and I want to be part of that," he added. "All the lads and the staff have been really good with me and I'm pleased I've re-signed and I can kick on again.
"I drive past the stadium every day and it's a massive carrot for us. The new stadium is something special and it would to be nice to go up via the play-offs and play League One football there."