I need someone to break down the steps with how I could make this piece of the chair on the other side of it. I’m not too familiar with the mirror modifier (I did try it, but it did not place the object where I wanted it to be placed).
Add an empty, then set is as the Mirror Object in your object’s Mirror Modifier. The empty will act as a mirror line. Next time search through the Blender manual before asking on a forum
Use mirror modifier and as a mirror object choose your chair. The char has to have the origin point into the center so that handler will mirror exactly along X axis as you want. If the origin point isn’t in the middle then use the new object > empty as suggested above. I suggest watch some video about mirror it is easy modifier and you will get it fast, as well as to know what is bisect and flip for.