Right now there is no common functionality to find installed version of modules from marketplace.
Most of the marketplace modules handle showing their version differently (e.g. creating folders containing name within the installed module – see module “CommunityCommons”). There is no similar way on how to find the version, which makes the User Experience really bad.
A lot of people are using workarounds and store the versions manually in additional files. This is a lot of effort and pretty risky (e.g. when forgetting about updating these lists).
It would be a huge improvement to have an overpage in Mendix Studio Pro which is showing installed marketplace modules including the current version.