my old hard drive is the IDE power cord interface ( 4-pin). Now the hard drive had bad, and I want to buy a sata power interface. My motherboard has sata interface, but I don't know how many pin the sata hard drive interface to connect the power supply interface. Could I use my old power supply?

There are adapters available that convert from Molex (4-pin old style) to SATA connectors.

my old hard drive is the IDE power cord interface ( 4-pin). Now the hard drive had bad, and I want to buy a sata power interface. My motherboard has sata interface, but I don't know how many pin the sata hard drive interface to connect the power supply interface. Could I use my old power supply?
Serial ATA - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/SATA#Power_supply)
There are 3 voltages 3.3V, 5V and 12V


There are adapters available that convert from Molex (4-pin old style) to SATA connectors.
Yes but only the older SATA drives can run with only 5V and 12V

The Seagate I got this Christmas came with a slip of paper in the box that says "requires 3.3V to operate. Failure to supply 3.3V may damage device"