All you need is a step down transformer. See the note next to the power plug at lower right. It specifically says that it's designed to work with 50 or 60 Hz power.
However, my preference would be to replace the whole power supply in the lower right corner with a off the shelf modern DC supply, if you can find something that puts out 130 V or can be adjusted to that. That takes care of isolation, the rectifier tube wearing out, and the inevitable hum this amp has on the output.
But, it's not quite that simple. You then have to find a way to run the two fillaments and the indicator lamp. It seems the filaments are 45 and 20 V, for a total of 65 V in series. That doesn't quite add up with the 200 Ω resistor dropping 20 V due to 100 mA thru it. That only comes out to 95 V instead of the expected 110 V. This is probably due to filaments being rather forgiving in voltage. With 110 V applied to the resistor and filaments string instead of 95 V, the filaments get a little hotter than nominal, but probably not decrease tube life significantly. Another possibility is that the filaments don't really both want to run at 100 mA. Putting two dissimilar filaments in series is rather a hack. This was done to not need a large and expensive power transformer. Perhaps the somewhat higher than stated voltage is due to one of the filaments just getting the minimum at that voltage.
One option with a 130 V DC supply is to just increase the 200 Ω 5 W resistor to get the indicated 100 mA thru the filaments, or the intended 65 V across them. Again, check that each filament gets at least its minimum voltage. A more modern option is to make a small buck converter that reduces the 130 V to 65 V to run the filaments from. You can still be retro and waste a lot of power by running a LED from that with a suitable series resistor. That LED replaces the neon bulb.