What's the supply voltage on that PSU?, if 24V then you're cooking (that's the supply voltage to an AXBB-E). You'd have to re-spin the cable assemblies to the stepper drivers (the green/blue/purple/brown cables) - cut the ends off where they connect to the USB BoB, and re-terminate into your assigned Step/Dir signals from the AXBB-E. There's a 4/5 pin connector next to the stepper motor connectors which I expect carries the limit/home switches - they'd have to be re-terminated into the AXBB-E inputs, and you'd need to examine the E-Stop wiring to work out if it's acting as you want it to act (you don't particularly want to switch off the AXBB-E every time you E-Stop), but it's not a particularly difficult conversion.

For me, I'd start with the AXBB-E outside the box, slave power to it and transfer one stepper driver to one pair of outputs, commission that, rinse-and-repeat. Once you're happy then install into the enclosure and make good.

All do-able... if you want to throw the cost of an AXBB-E and UCCNC license at it.