Encode UTF8 with Polish Characters

I would like to convert and TArray to FString and encode it from UTF8.

What I Have:
TArray that contains special character, example:
As you can see in array on position 191 to 196 there is a character \u0142

I would like to change it to a corresponding character: ł
After using UTF8_TO_TCHAR on that array I got a string that contains phrase u0142. What do I need to do to encode it correctly?

Have you gone through this page?

At worst, you could decode all the characters into UTF-8 code points (int values basically), swap the character, and then re-encode them as a multi-byte char string and write that out.