Samsung SSD 850 Evo drive

What newer iMac are you wanting to put it into?

FWIW

1) newer iMac are sealed units and not as ease to work on.

2) many of the newer iMac's can not take a 2.5" SATA SSD.

3) it might do better to put the SSD into an external box.

OK

Best bet is to just get a 2.5” external drive enclosure to put the SSD into.

With an older Mac 2012 - 2015 iMac, an enclosure with USB 3.0 is your best bet.

If you end up with a 2017 or newer iMac, an enclosure with USB-C is a good option.

If I were going to replace the drive in my Mac, which I actually did, I'd never even consider an old, used drive.

If you're going to the trouble of opening it up, which may be more difficult than you know, use a new component and put the old brive in a USB enclosure to be a dedicated backup drive maybe.

Depends on the year model. A later iMac can not boot from Snow Leopard, but you can access all of the user data on the SSD and/or upgrade to a macOS that runs on the later Mac.