You can check which version of J2Commerce you are using. Just Go to J2Commerce > Dashboard where you can find the version of J2Commerce. Please refer the image below.
How to upgrade the J2Commerce Free version to Pro version ?
If you have a login and you are in the subscribers list, please go to this link: click here
Download the J2Commerce Pro Package.
Once you have downloaded, go to Joomla installer and install the J2Commerce Pro Package over it.
**Note**: By installing the J2Commerce Pro version over the Free version, your content will not be lost.