Which version of the Gmail app do you have? When you select an email and tap the 3-dot menu button at the upper right, you don't see a Snooze option there?
It is the latest version. I am able to get the new features using my personal account, but when I switch to my work account, these updates disappear. At work it is showing the snooze option on the web Gmail interface.
Oh, I see that now as well. It must be a limitation with non-Gmail accounts on the Gmail app. Not every Gmail feature from the web interface is available on the app, so this must be one of them. Send some feedback to Google through the Gmail app's Help & Feedback menu option and let them know it'd be nice to make it available.
Give "Google inbox" a try, that's has a lot of features similar to the new Gmail including the snooze function. You can run the 2 side by side to see if it meets your needs.