If you try to plot a drawing and see only .stb files in your plot style pull down list. You need to change which type of plot style table, color-dependent or named, is used in a drawing.
You can use the command CONVERTPSTYLES to change which type of plot style table, color-dependent or named, is used in a drawing.
When you convert a drawing from using color-dependent plot style tables to using named plot style tables, any color-dependent plot style tables attached to layouts in the drawing are removed, and named plot styles are attached in their place. If you want to use the styles defined in the color-dependent plot style tables after you convert to using named plot styles tables, you should first convert any color-dependent plot style tables to named plot style tables.
When you convert a drawing from using named plot style tables to using color-dependent plot style tables, the plot style names assigned to the objects in the drawing are lost.