Ok, I'm assuming this drive has an SCA80 connector, since you said it has no dedicated power socket. Get an SCA80 to 50-pin SCSI adapter like this one:
http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 5721284086
This will give you the standard 4-pin Molex power connector, the 50-pin SCSI connector your Emu uses, and jumpers to configure SCSI ID, termination, motor start, etc.
Now here's the IMPORTANT part: you will most likely need to install a separate power supply for that hard drive, as it will draw too much power and burn your Emu power supply out (especially if your Emu was made before September 2001 and thus has the weaker 43W PSU; newer Emus have the stronger 65W PSU).
In my Emu I used a Sunfone dual voltage universal power supply (basically the PSU bundled with LaCie d2 external drives; $17 new from LaCie). This PSU takes between 90~264VAC and puts out 2.2A at 12VDC and 2.0A at 5VDC. This will allow you to use any drive you want in your Emu without worrying about burning it out.
IMHO it would be much easier for you to just get the SCA80 adapter, an external SCSI enclosure, and use the hard drive externally. It won't make any difference to your Emu and it will be much safer and less problematic to do.