The base module LTMR can give you only current and time-related variables.  For reading voltage, energy or power-related variables it is necessary to add expansion module LTMEV40.. to your LTMR.
Register addresses can be found in LTMR – xxxx manual (where xxx is Modbus, canopen, profibus Ethernet or devicenet).
Except the canopen and devicenet that uses index/subindex or devicenet addressing, all the other communication uses the same logic addresses.
So if you open LTMR – Modbus manual, the list of registers starts on page 32 (with datatypes description), and the logical addresses 0-1399 are on pages 39-60

For reading the measurement we have to look into monitoring variables, to be precise to measuring variables, addresses 465 – 539.
However there is one exception.
The active and reactive power consumed is not in this group of measurement variables. They are in the group of “monitoring statistics” which are addresses between 122 and 149.
So active power consumption, with the unit 0.1kWh is situated on 2 addresses, 143 and 144. The value is stored as unsigned double integer, means 32-bit unsigned value. Reg 144 carries lower 16bits, reg 143 gives  higher 16 bits.
Manual being referred is DOCA0130EN-00, 07/2017

Released for: Schneider Electric Egypt and North East Africa