If it is a restful API, you must use Restv2 connector, and if it is SOAP-based API, WebService (WS) consumer connector should be used.
You can refer to the connector guide below
WS consumer connector- Web Service Consumer Connector
Rest V2 connector- REST V2 Connector overview
Please let me know if any queries.
WS consumer Endpoint URL for the web service. The WSDL file specifies this URL in the location element.if that specification is not there,you can use the REST V2 connector using the endpoint create swagger file