The drive is still in the casing that it was in when in the time capsule
The drive sits in the TC with a few rubber blocks.. you must have removed the top plate and the SATA plug to get access to the drive.
Just lift out the drive.. with all the cables out of the way and the SATA cable removed from the back of the disk and carefully hold the ribbon cable aside so you don't tear it. The drive should just slide out..
If you have not yet looked at ifixit site do so ..
Airport Time Capsule A1470 Hard Drive Replacement - iFixit
There are endless variety of USB to SATA disk boxes available.
I would just use eBay .. search for USB 3 SATA adapter
Orico are not so bad.. avoid some of the really no brand names.. the power supply in particular tend to be poor quality.
Or you can get a dock. They come in solid metal, plastic of all different colours, or even transparent which is cool.
ORICO TRANSPARENT 2.5/3.5 inch USB 3.0 Hard Drive Dock PRODUCT REVIEW - YouTube
You can also buy these things from OWC in US.. they have specials all the time.