Could you please post the exact error message you are getting? That way we can see what exactly is wrong with the version number (since it could be one of several issues). Wording instead of a screenshot would be preferred (since we don't have image uploading on this forum, and it takes some time for the forum mods to approve links outside Apple sites).
The iOS version numbering system is not very clear in the documentation (https://developer.apple.com/library/content/technotes/tn2420/_index.html), so I'll try my best to explain. There are two numbers both controlled by the developer in Xcode: version number and build number. The version number is displayed in the App Store to your users. The version number of your .ipa should equal the version number in iTunes Connect. The build number is a unique version number for a particular build (.ipa), and every build you upload to iTunes Connect must have a different build number.
Here's how to check the version numbers of the .ipa file:
1. IMPORTANT: Make a copy of your .ipa file in Finder with Right-Click > Duplicate.
2. Right-click the copy and click Get Info.
3. Under Name & Extension, change the .ipa part to .zip.
4. Click Use .zip.
5. Double-click the new zip file.
6. Open the new unzipped folder.
7. Open the Payload folder.
8. Right-click the only file and click Show Package Contents.
9. Double-click Info.plist to open it in Xcode.
10. Look for the key Bundle versions string, short. The value of this key is the version number that should match the number in iTunes Connect.
Screenshot: https://developer.apple.com/library/content/technotes/tn2420/Art/tn2420_infoplist.png
If the version numbers in your build and iTunes Connect do not match, you will need the developer to provide a new build with the correct version numbers. For now, I would not worry about the build number.
Once you successfully upload the build, you can select it in iTunes Connect. Keep in mind that it takes time for iTunes Connect to recognize your uploaded build (around 5-30 minutes in my experience). Screenshots:
https://developer.apple.com/library/prerelease/content/documentation/LanguagesUtilities/Conceptual/iTunesConnect_Guide/Art/9A-AddBuild_Annotated.png
https://developer.apple.com/library/prerelease/content/documentation/LanguagesUtilities/Conceptual/iTunesConnect_Guide/Art/9A-SelectBuild_2x.png
Then, click Submit for Review.