I suggest you modify your request to request the 4000 addresses you need, but you must request 2 registers (16-bit) for one of the 7000 values (32-bit floats).
Notice in the table in the extract that Urms L1is locatedat 7000 or 4000, while Urms L2 starts at 7001 or 4002 (2 16-bit registers are needed to transfer a 32-bit float value).
Once you have registers 4000 and 4001 in the pLC, transfer them to a 32-bit register (such as MDxxx) and read them as a floating-point value (REAL datatype).
If you have a numerical value and it makes sense, you are OK. If you have a numerical value and it makes no sense (such as -1,234 e-34) then you have to invert the recived bytes (see the definition of float and sfloat registers in the Lumel manual:

Register bytes of float type are sent in 4321 sequence

Register bytes of sfloat type are sent in 2143 sequence

Hope this helps,
Daniel Chartier