To find the currently running version, open UTM and in the menu bar, navigate to UTM → About UTM. The version and build number will be shown in a new window.
To find the currently installed version, open UTM at least once (after installing the version you wish to find). Then, close UTM and open the system Settings application. Scroll down to the entry for “UTM” and select it. At the end of the preferences, you should see the version and build number.
WIP Currently, exploit installed UTM builds do not have the preferences entry.
If you do not see the version and build number but you do see all the UTM preferences, your version of UTM is too old.