You will find the version in Menu > Help > About.
What notification are you receiving?
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If it is about the Contacts API is being deprecated, you will need to upgrade to at least 8.2 or later if you are using an older version.
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If it is about the value did not match the regular expression ^people/[^/]+$. go to the Contacts section of eM Client, then by right-click on the Gmail Contacts folder, choose Properties > Repair > Repair. This will resync the contacts with Google and the error should disappear.