SSD drive to USB connection I have a spare SSD Drive that's been removed from my iMac. Is there a way I can use it externally using an adaptor or something though USB?
Yes, this is possible by purchasing an appropriate external case or "enclosure". You just need to make sure it's one suitable for the SSD you have.

These cases are not hard to purchase. You can get them from eBay, Amazon, etc. Purely as an example, here is a link to one on macsales.com.

NOTE: The one in the example is for Mac SSDs used from June 2013. As I said, be sure you get the correct one for your SSD.