I would probably start by trying to isolate stuff if you can before I’d worry about upgrading all the cables.
Hard to judge as I don’t know what the setup is but if it’s your guitar going through a bunch of stuff and ending up at a USB input device then I mean you start by just plugging some instruments in directly and seeing if you can hear the hum, particularly if you bring the gain up a lot. (I say some because obviously if you’ve only got one instrument it could be a fault in that instrument so good to check with a few if possible.)
So you would just build out from there and hopefully at some point you plug in the cable, pedal or device that’s bringing the hum to you.
If you are running pedals off the mains I’d try running them off batteries as mains stuff might bring this kind of effect in from what I remember.
I guess you may find it’s just ‘there’ and you can’t do much about it (maybe there’s a bad earthing in your guitar pickups or something)
I guess you could also look at doing some kind of compression/low pass filter on your recordings too that would likely mask the hum if you can’t find a good way to get rid of it entirely.