Salesforce Connector supports the Salesforce API version 35.0 by default. The default API version could change depending on Salesforce connector release.
The version of the Salesforce API affects which data types are supported Exemple:
If we want to load data of data type such as Geolocation which is supported by API version 30.0 or later, and then in the connection string we use an earlier API version e.g API version 29, fields with Geolocation data type will not be accessible.
The cause is that, there are tables that can't be accessed with the API 29 and thus requires for example API 35 or API 30.0 and vice-versa.
A solution to such issue is to use two different connections string in the same document (the first connection with API 29.0 and then the second connection with API 38.0 or 35.0 for example).
To change an API, please follow the instruction provided on online, section 5 i.e. “connect to an alternative Salesforce.com environment
URL (optional) is used to modify an API