Many of use use laptop, during a situation we might hold a internal Hard Disk drive just as spare, in that case an internal HDD is cheaper compared to an External HDD than purchasing a new one.
It’s easy to convert with an Enclosure plastic case with closed circuit ready with USB connection and a cable.
The most reliable Enclosure Case is manufactured by WD (Western Digital). Internal HDD sits exactly into it to the edges.
It costs around $5.5
Finally your External HDD is ready to use.
NOTE: Make sure you use this as a fragile device as this meant to be soft use.
E.x. I have been using my Internal HDD 1Tb since 4 years for all my needs with soft handling.