I have Nexus Repository Manager OSS 3.13 but it looks like some feature like Staging, Tagging is only available with Nexus Repository Manager Pro production for which license is required.
Hi Vish - Licenses are available by purchase. I would send an email to sales@sonatype.com to get in touch with someone that can help you determine the cost.
You can check out what other features you would get with a license here: