Unfortunately, digitec's answer is not correct. The extension does not come with a Hue Connector. Only the basic kit (with the mains adapter) includes one. The extension only comes with the connecting cable to connect 2 uncut strips together.
The Hue Connectors are not available individually, but Litcessory has interesting connectors on sale. Unfortunately not at digitec/galaxus either, but you can find them with Google.

The light strip extension is part of the scope of delivery, unfortunately these cannot be purchased separately in our shop.