The new 27 inch iMac I gave to my grandson a while ago, is now back here. He built a couple of amazing PCs, and now has no use for the Mac.
I want to give my 24(10.5.

inch to my husband, keep the other new 27(10.10.5), but want to transfer some apps, only a few documents, all the music, and pictures to the one which just arrived.
I put it back to factory new, so its empty at the moment of any of my stuff.
I just bought a Seagate 1 TB ext HD, but I dont want to transfer everything, just pick and choose.
Is the best way to do this, to copy the entire hard drive, pick out what I want before I plug it into the 27? Or to put into a folder only what I want to transfer, copy that, then move it?
The apps on the 24 are rather old, and I want the apps from the new/other 27 instead. Assuming that I can transfer those at a later date.
Sort of complex for my old brain, but I know you people here will have a good way to suggest for me to do this.
Thanks in advance,,,,,,,,
Then we will have a few Macs and a PC or 2 to donate to the guy who fixes up computers for the kids in the high school who cant afford anything.