As Dave said, it is about 1/113th the size of the moon so at 113 power it should appear as big as the full moon does to the naked eye.

Always start with your lowest power. That will give you at least a 1 degree fov. So if your finder is adjusted correctly Mars should be near the center when you look in. It will be very bright. Almost too bright. Then start increasing the power until the image begins to break down then back off to where it was still clear. There's nothing around Mars nearly as bright as it is so you'll have no trouble recognizing it. It far outshines the stars of Orion, Gemini or Taurus that are its neighbors. Could you have been way off target and looking at Aldebaren or Betelgeuse? Both are bright orange stars in the area.

Use the moon to check your finder alignment. By day you can choose some object along the horizon that stands out above it like a tall tree, steeple or power pole. Scan the horizon with the scope until you find it then adjust the finder to match. I used to align a lot of finders for folk at Hyde Memorial Observatory. There was a University clock about a mile away that had an illuminated dial at night. It was a perfect target for finder alignment. You need something unmistakable like that that is on the horizon so you can quickly scan and find it.

Rick