How to get an old Android app

In May 2013 I bought a NAS P/N: WDBAGCG0010HCH-00 (1000 GB 3,5"). S/N: WMAZA4467238. It is still running like it should. No problem. But…
At that time there was an Android app that I used on my phone and on my tablet. One day I had to reset the whole thing and since I did not use the access from my mobile devices I did not install that app on them anymore. Then time goes by.
Recently I decided to initiate using that app again. The one I once had did not show up in Google Play. But, there is one called ‘My Cloud Home’ v.3.6. However, when I start that app, login, seek for the NAS, finds it, and then it asks me for a code MMM-MMM-MMM which should be on the label that is on the side (in my case bottom) of the NAS. Well… there is not any. Below the MAC there is nothing.
My guess is that this is an app for new NAS unit and not for that 10 year old one that I have.
My questions is: is there a work-around or is the old app dowloadable somewhere?

[quote=“Captain7273, post:1, topic:287929”]
WDBAGCG0010HCH-00
[/quote] A search after highlighting the product number you provided brings up My Book.
WDBAGCG0010HCH-00 - Search (bing.com)

@Captain7273
Do you own a My Cloud Home or a My Book?
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Hi, its a WD My Book “Live” indeed.

I just found out here that the time for trade in has expired on September 30th 2021.
The procedure is a bit silly, if it had still been valid. The MBL is loaded with data and it would have been more elegant if one first gets the new unit and afterward sends the old unit back to WD. I’ll keep mine in service as long as it works and have found other ways to save my data.
Understandable but a pitty that the old app is no longer available.

@Captain7273
I am doing the same with my old first generation WDMYCLOUD OS3. It will not update to OS5, so I have it set up for use on my home network. I will continue to use it as long as it works.

I do have a second generation WDMYCLOUD OS5 in use.