There are 2 two types of DataPower gateway as mentioned here. I have installed the VMWare version provided with the installation package. How can I know whether I have "DataPower API Gateway" or "DataPower Gateway (v5 compatible)"?
DataPower is a separate product and comes in its own "package" and version.
When you install/setup API Connect you can chose which version of API Connect configuration on the DataPower instance you want.
The v5 compatibility is only for older DataPower appliances (XB62, XI50, etc) and since you are using VMware, just install the latest DataPower version and then use the API Gateway version.