Connecting the [ 5V and G(round ] pins in the top at the right should do the trick.

For power you can try to find one of these (or solder your own version).
https://vesard.com/525-Zoll-Molex-Adapter-mit … hluss-fuer-LEDs

The two rows at the bottom seem currently to be jumpered for 66 continuously.
The four pins in the middle at the left are likely for the '100' digit.
Here is a layout for variations:

You can hook up the power to a 5 volt battery (or a three pack of 1,5 volt) for easier working with it.

The three pins in the middle on the right [ L - TL - H ] are for connection with a turbo switch - the original turbo switches looked like this:
http://www.suntekpc.com/htm-2/power-switch-pu … urbo-3p3c-2.htm

Thank you for the help. The adapter you linked though seems to be 12V one if I understood correctly. Is there any place where I could buy a 5V one?

Red colour for 5 volt wires is not universally applied in aftermarket adapters as far as I have seen. When you have one with yellow wires (or red for that matter) you should check out if the Molex pins correspond with the red wires of your system to be safe. If you happen to have a 12 volt adapter it is easy to rearrange the pins so that they connect to the 5 volt pins of your system.

I didn't really look at the color of the wires, I just looked at the which side of the molex connector the 2 wires are in the adapter that you linked and it seemed to me that they were on the 12V side. I have never taken a molex connector apart myself. I have some molex connectors that have a fan connector attached to them, but those fan connectors seem to be on 12V side too as far as I see.

When you want to reposition the pins in a Molex connector all you have to do is pull out the pins and put them where you want them to be.
With a small screwdriver you can push the two 'wings' of the pins a little bit to the inside and subsequently with bit of wiggleing and pulling on the wires they will come loose. You can also use a small fitting tube, like for example the ink reservoir of a ballpoint - push the tube over the pin, wiggle a bit while pulling at the wire from the other side of the connector and it will come free.
Alternatively you can also buy a (presumably expensive?) Molex pin extractor tool set.