Correct. Look at the numbers under each eyelet. Right now the red wires are connected to 220V. So just move them to 110V. So red to center eyelet of the left transformer and then from there to the 110V eyelet of the right transformer. Same arrangement, just moved from 220V to 110V eyelets.
However, there is a potential issue. Because they are not split primaries, the power rating will effectively be halved. But I don't think it will be an issue. Those transformers look fairly large for what they're being asked to do. Each of those preamps probably draw maybe 100mA or so. So 400mA in total. And it looks like each transformer / supply board is identical so that would suggest that each is for 2 preamps. If I had to guess, I would say someone bought those as a cheap kit which means the transfomers are probably right for either 110V or 220V. But just to be safe, first check it without the load (without being connected to the unit) and check the voltages to see that it's working at all. Then, connect it to the unit and then, with the cover off, turn it on and listen for any hum. If the transformers are too small you might actually be able to hear it hum. If you hear any hum at all, that's not really good. If one get's hot, that's obviously a bad sign. Careful not to touch any of the exposed wires inside of course. Even after you turn it off, there could be some voltage that hasn't discharged (especially if there's no load attached). You can also check the output voltages with the power on if you're careful. If they dip by more than a 100mV with the load connected, that might be a bad sign. But I would say 90% chance it will work just fine (assuming it worked before you bought it).