ohmic state vs saturation state drain-source resistance of a MOSFET
The datasheet says Rds=3[mOhm] max. This means that when the MOSFET is in saturation (aka the Vds is high enough to open the mosfet completely) the Rds is no more than 3[mOhms].
The Rds therefore can be lower than 3[mOhms], but the datasheet does not guarantee it, nor does it provide a graph that shows how can you achieve lower Rds.

if we take the MOSFET get out of ohmic region and and make it
saturated by applying sufficient DS voltage

You mean by applying a sufficiend GS voltage? You can achieve saturation by changing Vgs, not Vds.
Thank you @Elliot Alderson for correcting me here, saturation also depends on Vds.
Increasing Vds does lower your Rds, but its just an effect of the mosfet, not something you really 'can control'. If you need a Vds=12V for your system to function, what will you do? decrease it to Vds=5V to get a lower Rds? Probably not. Therefore, driving the Vgs drives the mosfet to saturation.
The more Vgs you apply (without exceeding datasheet's limitations, which here are +- 20V) the lower the Rds, and the higher the Vds, the lower the Rds.
EDIT:
Ok so I now understand that OP wants to keep the Vgs fixed and increase the Vds and see what the Rds on is, untill he/she achieves a specific Rds on.
As mentioned here by @stevenvh

So, yes, \$R_{DS(ON)}\$ varies with \$V_{GS}\$, and yes, it's higher
at higher temperatures.
If your manufacturer can't give you the information and you really
need it, move on to another manufacturer.

If you really need this information, find another mosfet/manufacturer that provides it to you. Datasheets are not always perfect.