Upload a new build to a "Ready for sale" version?
Submit a new build with 3.4.1 as the short version value in the Info.plist file.
The value for CFBundleShortVersionString must change between releases. The three digit semantic versioning format is described in Apple's developer documentation and is widely understood beyond Apple's platforms:

Given a version number MAJOR.MINOR.PATCH, increment the:

MAJOR version when you make incompatible API changes,
MINOR version when you add functionality in a backwards compatible manner, and
PATCH version when you make backwards compatible bug fixes.

Additional labels for pre-release and build metadata are available as extensions to the MAJOR.MINOR.PATCH format.