Using PSE Albums with icloud & apple devices

[etaf]

Working on a problem for a friend

Background

Part 1 - PSE
we are planning on purchasing an imac and buying PSE for OSX
then I will be able to backup all the catalog with Albums Tags etc and restore onto the iMac
I know that works as i was able to try that out in a shop recently
I would then have 1000's of photos in 100s of albums onto the iMac and get rid of the windows PC

So thats solved above

part 2 - icloud
going forward he will be using an iphone for all his photos and droping the compact camera
And the Photos App works really well and gets everything into albums which he uses all the time

Part 3 - the issue
a) We have PSE with albums on the iMac
b) We have Photos and icloud with loads of albums on the iphone (256GB) and sync across to an ipad

Happy to drop PSE - but how do i get PSE to work with icloud , so we can get all those albums onto the iphone and ipad and still use icloud photo library going forward

He just wants all the OLD Legacy photo Albums and all the NEW photoo albums available on all devices
iMac, Iphone and Ipad

thanks