If it gets its power from the USB port it will be a 2.5" - just a standard notebook drive in an enclosure.
Tips for keeping an external drive healthy (also applies to flash drives, SD cards et. al.)
Try not to plug them in when the computer is powered on.
Because a USB port supplies electricity, a worn port or plug could arc. Hard drives may be OK (just the SATA-USB adapter blows) but it's usually fatal for a flash drive.
Always use safely remove.
Especially if it uses NTFS, windows will have lots of files open, even if you don't use the drive (e.g. $MFT).
It also helps because windows cuts the power to it, less chance of arcing.
Don't move the drive when it's spinning.
Hard drives only, since the heads just skim the platter, any movement could cause a head crash, usually fatal.