Hi ismailcetin,
you can convert coordinates using Lisp functions built into Autocad Map. What version of autocad are you using? If you are on subscription I think Autocad map is included.
To convert a single point you need to use
ade_projsetsrc
ade_projsetdest
ade_projptforward
Let me know how you go. Happy to help more if I can.
Cheers, Rod