Hello @Sera Nur DARKILIÇ ,
it seems you have created a Free Azure IoT Hub and you want to make use of multiple routing endpoints.
The Free tier has a limitation of just one routing endpoint (see 'Additional endpoints').
If you want to make use of more endpoints, you need to move over to the S1 tier which offers 10 endpoints.
As an alternative, you could make use of custom logic in an Azure Function to accomplish the same.
Send all incoming messages to an Azure Function and route them there:
Consumption plan pricing includes a monthly free grant of 1 million requests and 400,000 GB-s of resource consumption per month per subscription in pay-as-you-go pricing across all function apps in that subscription