Within the Moodle interface, you will find the plugins management area in the administration block.

In the Administration block under Site administration, expand the Plugins section. This brings up three things: a link to Install plugins, a link to the Plugins overview page, and the expandable list of the top level plugins areas in Moodle.

Click on the Plugins overview page and it will bring up the list of all installed plugins, including the Plugin name, Source type, Version number, Release number, Availability, Link to Settings if available under Actions, Link to Uninstall, and any Notes related to the plugin such as dependencies.