Our developers are using version 184.108.40.206 so we need to upgrade to the same level. Only 220.127.116.11 is available to download in the site
If you need older Versions you have to contact support
Ref: Downloading Old Versions of Nintex Workflow And Forms For SharePoint - Nintex Knowledge Base
As far as I know there is no repository where you could download specific versions of Nintex Workflow. Also as a lot of bugs have been fixed since 18.104.22.168 I don't think someone would advice it to stick to that version. If your developers don't have a really good reason to stick to that version I strongly suggest you upgrade to the latest version (which supports all features of 22.214.171.124 anyway).
If you really can't go with anything else than 126.96.36.199 I can give you a link to download it but I suggest you speak with your developers first.
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