How do I see number of or icon for unread messages?

My device: I use Android 9 on samsung galaxy s9.

Background: I believe there was a feature before (or maybe currently still, but I turned it off) about showing number of unread messages on apps like whatsapp, viber or the SMS app (and i guess gmail or facebook) or at the very least there's some kind of dot or something on a corner of the icon of such an app that indicates there exists at least 1 unread message (so the dot is an alternative to a specific number of unread messages).

My situation: I do not have such number or dot on icons on apps on my device. If I get a message on whatsapp or viber or regular SMS but say I have to install some updates and so my phone has to turn off or restart, then the notification of this message is gone.

Question: How do I see number or existence of unread messages on icons of apps such as viber and whatsapp and the SMS app?

I have tried looking this up, but

1. I wasn't able to find any articles specifically on Android 9 and Samsung Galaxy S9.

   
   



2. The solutions proposed in articles I've found on Android 9 but a different phone or on different versions of Android have not worked for me.

   
   



3. I've tried looking up some apps on the play store, but I haven't downloaded any because of the reviews.