Replace question mark within a word

I am getting HL7 messages through with question marks characters in the middle of words like "can?t and dc?d" and I want to replace them with apostrophe. I was able to replace character (?) at the beginning of the sentence using mystring.replace(/^\?/,"-")

I tried mystring.replace(/['\x3f']/g,"'"); but the problem with this one is it converts all questions marks.



Thanks in Advance

Replace question mark within a word