If I use a sata internal drive with a sata/power to usb adapter and connect it to a usb port outside my PC would I be able to use that as an external HD without issues?
However, I recommend you buy an external hard drive enclosure instead of an adapter kit. Enclosures come with an a/c adapter and internal connectors for the drive's data and power connectors, and the enclosure provides a fair degree of protection for the hard drive rather than having a bare drive sitting on your desk or table.