There are about eight different ways to assemble the raw registers and bytes into a 64-bit word.
I would recommend first finding out the byte pattern for your source device.
You may be able to read the 4 registers as 64-bit uint, or you might need to read as 16-bit uints and assemble parts into your 64-bit word in the required order…
Then find a java IEE (presumably?) decode for the float data.