The DGL 4100 is not a WiFi Router. If you want to go WiFi, you will have to get a WiFi router. The link Winfrey provided is a good comparison to your router. They are very old technology from 2005. The new ones are MUCH more secure and faster to boot.
If you want to stay with D-Link, this is an example of a wireless router that also has 4 ethernet ports for wired connections. So, if that's what you want, you could continue to have all 4 of your devices plugged in to an ethernet port. But if any of them are wireless (WiFi), you might be able to get rid of some ethernet cables. D-Link Wireless Router