How can I create ribbon storage for about 40 spools of ribbons?

You may want to line them up in a box. That way, each spool can be lifted out to use.

You can attach dowel rods on plywood and attach to wall.

If you are going to remove, just place them on their side in a bin or box so you can lift and replace easily. If you want to dispense ribbon, put on a dowel or tension rod. Affix in a box that will hold 20 spools wide, 2 deep. Then you can dispense the ribbon from the spool without removing.

How about a rod style trouser hanger. Spools slip on and off easily or you can dispense ribbon without removing the spools. Dollar store often carries these.