LN,
Thank you for taking the time to reply.
I can see my original description was maybe not the clearest I was trying to keep it brief and therefore a little less confusing, please read below I've tried to list it step by step for you.
I had iPhoto on my MacBook Pro, which was backed up running Time Machine on my WD MyCloud.
I lost my MacBook Pro through a crash, which I was unable to recover, or restore from WD MyCloud.
I was however able to access the backup to drag across my documents and the like, my old iPhoto library was one of them which I've copied into my Pictures folder on my iMac (Retina 4K, 21.5-inch, Late 2015) running High Sierra 10.13.4.
Now the confusing part is the above MacBook Pro incident was a good few years ago now and I've only just realised the backup on my WD MyCloud kept the documents and apps, just wasn't bootable so I'm now trying to recover the images on my iMac.
As this was a long time ago I've since started a new Photos library on my iMac and originally tried to import said iPhoto library using the option > open packaged contents > import library which I found on an Apple help page to assist with this.
This did not work and so I tried the iPhoto Library Upgrader tool also found on an Apple help page but when I access the upgrader app and search for iPhoto library it finds it in my pictures folder but greyed out and non accessible.
I understand this is a complex and overly confusing scenario and i've tried to list as clearly as i can.
Any help with this would be greatly appreciated and if you need anymore information please let me know and I will happily provide anything you need.
Daryll