These two connecting chains would fit this velo lock.

The lock has to be combined with a chain like this one in order to be used : https://www.galaxus.ch/fr/s3/product/trelock-chaine-dinsertion-zr-455-100-cm-antivols-pour-velo-10221056 . You then have to mount the lock on your frame for example, and attach the chain around a static element.