Now the question is, how can I connect the motor to delta connection
if I have only 400V line to line voltage?
If you have 400 V, use the star connection. There is no reason to use the delta connection and the motor will draw too much current and overheat if you apply 400 volts to a connection designed for 230 V.
Where can I get 230V line to line?
There places in the world where 230 V, 3-phase is available and not terribly uncommon, but if you don't have it and have 400 V, there is no reason to find it.
Is delta configuration only meant to be using with VFD in that case?
The delta configuration is for people that have 230 V 3-phase. However you could use it with a VFD if you want to operate above the rated frequency. You could probably go 25% above rated frequency and voltage, but the motor bearings and rotor balance are probably not adequate for any speed higher than that.