Power is carried on the cable itself. VCC could be +5V.
https://images10.newegg.com/NeweggImage/productimage/21-103-516-02.jpg?ex=2
This is a possible pinout. So far I haven't run into a document
for the MPF820 to confirm it. And no, it cannot be a "direct subset"
of the 34 pin, since one side of the 34 pin is all ground, and
one side of this has mixed power on it. One diagram I saw, somebody
only connected the VCC on pin 1 with some wire, leaving the
other pins open.
TABLE B-9 FDD Connector Pin Assignment
Pin Signal I/O Pin Signal I/O
1 VCC 2 INDEX
3 VCC 4 FDSELA
5 VCC 6 DSKCNG
7 VCC 8 READY
9 NOTCH0 10 MONA
11 LOWDNS 12 FDCDCR
13 GND 14 STEP
15 GND 16 WDATA
17 GND 18 WGATE
19 GND 20 TRACK0
21 GND 22 WPROTC
23 GND 24 RDDA
25 GND 26 SIDE
Buying adapters probably costs more than the drive itself.
http://www.cwc-group.com/c74972.html
And you'd want to check check and recheck that the
wiring is actually the right flavor. Since I did see someone
showing a diagram of a cable with "slight offset" which cannot
possibly work for a drive like this.
This one would be suited for connecting directly to the
motherboard 34-pin. You'd still need the $8 cable from
the other page though, to go from the adapter to the
bay where the floppy is installed. This thing is $10.
https://i.ebayimg.com/images/g/1~8AAOSwc49Y8MAj/s-l300.jpg
(
https://www.ebay.com/itm/1pcs-34-Pin-Floppy-Interface-to-26-pin-FFC-FPC-to-PCB-Converter-Board-Adapter-/262908814882 )
At this point, I cannot really guess at how many 26 pin standards
there are. There are at least two of them. There could be more.
Paul