It might be cheaper (and safer) to just get a new enclosure. Approx $25
On the left side you will see type of internal interface, select IDE, or sata.http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&N=100008040%20600006254&IsNodeId=1&name=3.5%22
3 1/2 in HDDs normally require +12 V and + 5 V. Most newer enclosure pwr pacs provide 12 V @ up to 2 Amps (24 Watts - most drives at or under 10 W) and the +5 is derived from the +12V. The unk here is does the required pwr adaptor suppy just +12 V, or both +12 V and +5V I have (or had) some power pacs that provided both. If you have the knowledge, you could open it up and check how it is wired. ie +12V and +5 V returns (Ground) would be tied together and the positive sides would go to 2 seperate circuits.