go to a trader and switch them around to free space again, and if You are filled totally just be happy about, there s no way to delete those You can only use them
For data you need a material trader in a high tech system.
There are three types of material traders. One does data, one does manufactured materials and the other does raw materials. You find them in high tech, industrial and refinery systems respectively. Use this tool to find where the nearest one is. type the system name where you are in "reference system".