Where to find version of installed component in Joomla system?

1. Check with administrator panel

If you have already installed component to Joomla system, then component version can be found on Control Panel page. It is usually located here:

ADMINISTRATOR > Components > {component_name} (For example: ARTIO Booking)

2. Check in file system (zip archive)

If you need to check component version before installation or installation was incorrect, then you can check zip archive: com_{component_name}.zip/{component_name}.xml (For example: com_booking.zip/booking.xml)
There should be similar tag to this example:

Please, replace {component_name} with text assigned to component.